I used to play Utopia many many years ago.  A friend was playing it more recently.
This is a text-based web MMO By the way, and not something you can really sit down for hours playing (you do have to check regularly though).

Otherwise I guess you could try the many short-ish Flash based RPGs out there.
If you're really really bored, you can try those Flash-based dating sims (and see how long you last without quitting).