I have been putting a page together showing all the Formula 1 grand prix circuits on OSM and this has shown how random motor racing circuits have been tagged in the past
Highway=road, Highway=motorway, Highway=track, Highway=service, Highway=unclassified, and leisure=sport have all be used.
Relations for the Grand Prix circuit have been created and where the circuit is a dedicated one the highway has been changed to raceway.
Annoying now I've been through the lot it seams that the highway=raceway tag has been abandoned (I could have sworn it wasn't last week) although Mapnik renders it (see Donington Park, Silversone, Hockenheimring, and Nürburgring for some old highway=raceways) - typical!
If you are in Montreal or Valencia and looking for something to map you could do worse than double checking the grand prix circuits out - looks like both are generally part of the local cycle networks and some areas are probably better tagged as something other than Raceway (current) or Track (previous) - in particular Valencia looks to have been redeveloped a lot since the aerial photography was taken and was originally laid down as a highway=track on top of open ground and other roads.
If you want to see how much stuff can be tagged round a Grand Prix circuit while bringing Potlatch to it's knees than the two German tracks are good places to check out!
Alas, not all tracks are in Open Street Map at present - 上海国际赛车场 (China), İstanbul Park (Turkey), Marina Bay (Singapore), 鈴鹿サーキット (Japan), Yas Marina (Abu Dhabi), and Korean International Circuit (Korea) are missing, and Wikipedia doesn't even know where the Indian track is (unsurprisingly all the new ones outside aerial mapping coverage).
Diary entry centred on the Nürburgring Nordschleife - where else could you do so really?
http://kjs.me.uk/osm/f1.php - shows all the tracks on this years and next years calendar (aside from India).