Miniclip is a vast flash game site that has hundreds of online games. There is a picture below of their full list but here are some of my personal picks:

http://www.miniclip.com/games/en/

Red beard - Good platformer
3 foot ninja - Nice litle platform roamer.
Cell Out - Kill the bad cells while keeping the good ones alive. This isn't the best version of this game i've found but it's freely available.
Gyroball - You're a ball. Get to the end of all the courses. The quicker the more points you get.
Crypt raider - Get blue blobs to the goal so you can get to next level. Gravity works so is similar to skull diggery in that sense :P

(Dont worry, image is only 32KB).