Yep, I carry such an adapter in my wallet, and one in the saddlebag of the bike. 1E each or so.

There's a 3rd kind of valve. Schrader is usually seen (over here, Netherlands) only on mountain bikes, Presta only on racing bikes. I estimate 90+% of bikes here come with this valve (Woods valve, aka. Dutch valve):



Picture taken from Sheldon Brown's site: http://www.sheldonbrown.com/gloss_u-v.html

Here's more discussion about the various valve types: http://www.sheldonbrown.com/brandt/presta-schrader.html