I feel that awards such as barnstars and other similar things are a great way to motivate users, and let them know their work is appreciated. Of course, so is a simple "thank you", but pictures are prettier. 
Please see WP:BSB. Or not. I go away for a few months and everything around here just falls apart, eh? My user page seems to have more outdated info and red links than... a... red link... farm? Oh well. The idea still stands.