(Many of these are referal links....it helps me out if you sign up via my link. :) )
Gods of Time
Kongregate has over 1500 games....most of which are a decent amount of fun. :)
Duels is for if you have 5-10 minutes a day just to accept challenges from other people and level up.
Gods of Time is a web based MMO....not a whole lot, but decent enough.