http://oldschool.runescape.com/
For those of us who spent hours and hours sinking time into this wonderful game, and then (at least I) was very sad to see it progress past the point of a simple, small browser game into a fullscreen mess. Old accounts do not carry over as far as I see, so you have to start from scratch.
Very good timesink though, fun to just leave it open while in game (either after youre dead, or during arty reloads).
For those who haven't experienced it, I highly recommend at least trying it out. It is slow and grindy, but takes almost no mental effort to play.