Android Auto, since being announced along side Android L in 2014 at Google I/O, has started to go mainstream. We've seen a slew of different after-market head units available with Android Auto, as well as many of the car makers also jumping on board. Google have made a change to their Android Auto website today, and is now listing the cars that are compatible with Android Auto. They are listing them by brands. So we have Audi, Buick, Cadillac, Chevrolet, Ford, GMC, Holden, Honda, Hyundai, Kia, Mitsubishi, Opel, Seat, Skoda, Vauxhall, Volkswagen and Volvo. Not all of these cars are sold in North America, but many of them are. Google also has head units from Pioneer and Kenwood listed. So if you're interested in getting Android Auto, this is a pretty good resource.
While it is nice to see all of the models available on one page, there is a discrepancy that needs to be fixed. For Audi's vehicles, they list the 2016 Audi Q7. Which does not exist, actually. Audi skipped the 2016 model year with the Q7, and instead have just released the 2017 Audi Q7 which does have Android Auto (which we got to test drive not too long ago and a review is coming very, very soon). Additionally, they list the 2017 Audi Q2. Which, unless Google knows something we don't - which is entirely possible - the 2017 Q2 isn't getting Android Auto just yet. Just the 2017 Audi A4 and Q7 (of which the Audi A4 will be available in a few weeks, according to Audi USA).
Google has also noted which cars will be getting Android Auto soon, and which ones are not quite available yet but will have Android Auto. Good info to have, especially since a car isn't typically something that people impulse buy. But they save up to buy and only buy once every 5 years or more. Seeing as a car is much, much more expensive than a smartphone or tablet. We also have all of these listed on our own Android Auto page, which you can check out and get all of the latest information and news about Android Auto.