Warning: this list is obsolete. Please check more recent posts.
Here is a further update on the 51 teams (27 Challengers, 23 Cruisers, and 1 Adventure car) aiming for the 2019 Bridgestone World Solar Challenge in Australia this coming October. Many teams are busy with construction, and below is my best understanding of the current team status (it does not yet reflect the to-be-published official list of teams). A few things have changed since my last list, and I have added some pictures and corrected some errors.
Meanwhile, 25 teams – Bridger, Calgary, CalSol (1st in 2017), Esteban (3rd in 2017), Florida, Ga Tech, Illini, Illinois St, Kentucky, Mich St, Missouri S&T, NCSU, NJIT, Northwestern, Principia, PrISUm, Purdue, Rutgers, SIUE, UBC, UPRM, UT, UVA, W Mich, and Waterloo, including 1 WSC team – are preparing to attend FSGP 2019 in America this July.
Recent BWSC news is that JU Solar Team have a body, that Eindhoven have a bottom shell, that Top Dutch and CalSol also have shells, and that Bochum have clarified their plans.
In addition, on 24–25 May, the Albi Eco Race will have Bochum competing against Ardingly and several French cars (see my report on the 2018 event).
Adelaide University

Challenger (Lumen II) – they have been doing a lot of testing.
ATN Solar Car Team

Cruiser (new team: see my team bio) – their team is a mixture of lecturers and students from five universities across Australia. They have tested a model in a wind tunnel.
Australian National University

Challenger (new car: MTAA Gnowee) – the car is named after a woman in Aboriginal myth who carries the sun. They are working on their mould.
Flinders University

Cruiser (Investigator Mark III) – they are planning to improve aerodynamics, reduce weight, and make some other changes.
TAFE SA 
Cruiser (SAV) – this time they will tow the trailer that belongs with the car.
Team Arrow

Cruiser (ArrowSTF) – they have done a six-month-out update video.
University of New South Wales / Sunswift

Cruiser (Violet) – they have been testing their car on the track.
Western Sydney Solar Team

Challenger (new car) – they won the American Solar Challenge last year (with their Challenger car Unlimited 2.0).
Agoria Solar Team (KU Leuven)

Challenger (new car: BluePoint) – they have some (top secret) production moulds and are now sponsored by Agoria. They held a mock race with the old car.
ETS Quebec (Eclipse)

Challenger (Éclipse X.I) – they came an excellent 3rd in the ASC, 102 minutes behind Western Sydney, and hope to go even faster with the new battery pack in their modified car. Planned improvements are summarised in their winter newsletter.
University of Toronto (Blue Sky)

Challenger (new car: Viridian) – they plan to unveil the new car in July.
Antakari Solar Team

Challenger (new car: Intikallpa V) – no news on the new design as yet.
Eolian AutoSolar

Cruiser (new car: Auriga ) – they will be back at the WSC after coming 14th in 2007.
Bochum University of Applied Sciences

Cruiser (thyssenkrupp SunRiser ) – Bochum is not building a new WSC car, but are improving their sexy 2-seater SunRiser, which came 3rd in 2015. They also have a solar buggy team. As in previous years, they are participating in the Albi Eco Race.
Sonnenwagen Aachen

Challenger (new car) – they have a car-racing game app starring their car.
Hong Kong Institute of Vocational Education

Cruiser (Sophie 6 plus) – they have been working on the car body.
R.V. College of Engineering

Challenger (new car) – no details as yet.
SolarMobil Manipal

Cruiser (SM-S2) – existing car.
University of Tehran

Cruiser (new car: Persian Gazelle 4) – they will unveil their car on 11 June.
Futuro Solare Onlus

Cruiser (new car: Archimede 2.0) – they have an exciting design concept.
Onda Solare

Cruiser (Emilia 4) – they won the American Solar Challenge (Cruiser class) last year, and they have written up their design process here.
Kogakuin University

Challenger (new car) – they have announced their participation and held a “Solar Team Welcome Party” for new members.
Nagoya Institute of Technology

Challenger (new car) – no news on the new design as yet.
Tokai University

Challenger (new car) – in January they hosted some visitors from Lodz.
Kookmin University Solar Team

Challenger (new car) – no news on the new design as yet.
EcoPhoton / UiTM

Challenger (new car: Tigris) – see their first vlog (in Bahasa Malaysia).
Mines Rabat Solar Team

Challenger (new car: Eleadora 2) – their new catamaran will look like this. They have made a mould for their body.
Solar Team Eindhoven

Cruiser (new car: Stella ?) – they have turned a shipping container into an oven for production and plan to reveal their car on July 4. The bottom shell just came out.
Solar Team Twente

Challenger (new car: Red E) – they are already producing regular vlogs (in Dutch), and have also produced an (English) day-in-the-life blog post. They have revealed their design, which is a GaAs catamaran (see the animation here). They will run a MOOC explaining the design of their 2015 car, and will reveal their 2019 car on (of course!) 21 June.
Top Dutch Solar Racing

Challenger (new team: see my team bio) – they have a shell, which looks a lot like Michigan’s Novum.
Vattenfall Solar Team (Delft)

Challenger (new car: Nuna X) – these are the champions formerly known as Nuon. See their 2017 aftermovie.
Lodz Solar Team

Cruiser (Eagle Two) – they have produced a solar baby, which is a prize that lasts.
PUT Solar Dynamics

Cruiser (new team) – they are making a mould for their body.
Singapore Polytechnic

Cruiser (SunSPEC 5) – they have new motors and new doors.
Chalmers Solar Team

Challenger (new team: see my team bio) – their final render resembles the car of the South African NWU team. They have been working on their suspension, and hope to ship the car in early June.
Halmstad University Solar Team

Challenger (new team: see my team bio) – they are planning a bullet car, much like Michigan’s 2017 entry.
JU Solar Team

Challenger (new car: Axelent) – they have a rolling test chassis and a body. The body design seems long and thin.
MDH Solar Team

Challenger (MDH Solar Car) – they have been doing some testing.
Solar Energy Racers

Challenger (SER-3) – they raced this car in South Africa.
Kaohsiung / Apollo

Cruiser (new car: Apollo IX) – they have been making some carbon-fibre seats.
Siam Technical College

Cruiser (new car: STC-3) – no news on the new design as yet.
Dokuz Eylül University (Solaris)

Challenger (new car) – they expect the new car to be 44% more efficient than the 2015 model.
Ardingly College

Cruiser – this high-school team came 6th in the iESC Cruiser class, but have upgraded the car since then. They have been entertaining royalty, and will participate in the Albi Eco Race.
Cambridge University

Cruiser (new car: Helia) – they are busy with fabrication.
Durham University

Challenger (new car: Ortus) – they have been doing outreach, as well as fabrication.
Appalachian State University (Sunergy)

Cruiser (new team: see my team bio) – as with some European teams, they have been testing at an airport.
Berkeley (CalSol)

Cruiser (new car: Tachyon) – they have a shell. They will also attend FSGP 2019.
Houston School District

Adventure (Sundancer) – this high school team from from Houston, Mississippi is a regular visitor, because they keep winning the US high school race.
Stanford Solar Car Project

Challenger (new car) – they have revealed their shell, which is a unique asymmetric bullet car.
University of Michigan

Challenger (new car) – they are asking for name suggestions for the new car.
University of Minnesota Solar Vehicle Project

Cruiser (new car: Freya) – they have posted a progress video on Facebbok.
This page last updated 23:09 on 18 May 2019 AEST. Thanks to Nigel for several news items.
Thank you for the update, Tony!
It looks like many designs are converging again.
Of course we are all curious to see if the top teams are coming up with innovations to stay the top teams. Will Tokai go for an MJ array this time? Is Michigan after breaking the curse of 3rd now ready for the final step? Will Nuna X still be a catamaran? What has the Belgian team up their sleeve? What sleek design will Kogakuin bring this time? Will Western Sydney continue their move up? What will the teams do that are returning after skipping one or more BWSC’s?
In the Cruiser class I hope we will see more competition than last year.
I am gradually warming up for the reveals, speculations and of course the race.
Erik
Those are all very good questions, and I’ve been asking them myself.
I am a Polytech Solar Team (Russia) member, we will not participate at WSC, and we don’t design a cruiser car. Perhaps we will go to ASC 2020 with a challenger, but we are not sure yet.
I’m sorry, I must have misunderstood something on your social media. I have edited the list. It’s a pity that you won’t make it to Australia, but perhaps 2021?