Another fun game for you - Portal: The Flash Version. This time, a flash version of Valve's Portal. For those of you not familiar with it, you have a device which allows you (or anything else) to open two portals which let you pass through the first and appear at the second, which given a 4th dimension (well, the flash version is only 2-D, so in this case a 3rd dimension) to moving around gamespace. It starts off quite easy and progressively gets harder. And it's probably worth playing with a real mouse, not the crap touchpad on your laptop.

Thanks to Imran for reminding me about this!