I thought, not very in depth of course as there'd be some major issues, about the possibility of user created quests. Probably just dungeons, branching off from a notice board in the local inns/pubs.
Users could have access to a cut down version of the world builder with a couple of "sets" and tack together a few rooms with some non-voiced triggered flavor text etc and mobs. To help game balance XP for all user generated contect would be set to ZERO but it would be more for the fun and exploration that for anything else. Would also provide a great creative outlet for some players.
World builder access or the ability to post to the notice board could even be in the online store perhaps?
Failing that, I've always been a big fan of the old Bards tale "dungeon under the pub" routine. Hack and slash at its finest for those with only a very few minutes to spare. What chance a randomly generated setup under one of the market pubs for the occasional fun time... even just a winding set of corridors running to one end room... or some such.
Edit: Sorry - missed this current post on random dungeons... apologies: http://forums.ddo.com/showthread.php?t=220345