Haven't bought any yet but the "Arduino Pro" comes in 168 and 328 versions each with 3.3V @ 8MHz and 5V @ 16MHz for a little less than 20 bucks at Sparkfun. 
Haven't bought any yet but the "Arduino Pro" comes in 168 and 328 versions each with 3.3V @ 8MHz and 5V @ 16MHz for a little less than 20 bucks at Sparkfun.