Just to echo everyone else who has banned that friv games website. From the few games I tried on it, not one was educational when compared to the likes of bitesize which we do allow the kids on. The games on that site are what I would call timewasters and no relevance to any subjects taught at our school.
Been meaning to post this one for awhile. Its basically a proxy that's software based rather than website based so it can be installed onto a pc or ran from a memory stick. There are some videos on youtube showing how it works.
This is apperently a educational games website but i don't see how pacman is educational, apart from history :-D