I've been working on a random dungeon, mostly for my own amusement but also with an eye towards using it when my group finishes Keep on the Shadowfell. This campaign ends when summer ends and everyone goes back to school, so I don't want to get to in depth and do my usual plot-arc wrangle, but we're going to need something to do after they finish the module. If the dungeon turns out interesting enough, and I don't think of anything better, I'll use it.
It's the first time I've generated a fully random dungeon. I started out with 3rd edition, which has charts for randomly stocking dungeons with critters and features, but no map tables. I got the AD&D Dungeon Master's Guide partially because of the random dungeon charts in the back, but was pleasantly surprised to find that the 4e DMG also has a nice set of charts.
I've been using those, because they generate the assumed size of rooms, but will probably refer to the AD&D charts for at least a couple of levels, as a change of pace. And I'm going to use the AD&D charts for weird noises and laboratories and so on; the 4e charts are even worse than the 3.5 charts in that area.
It's fun. Even without occasional re-rolling ridiculous or uninteresting results, there's enough decision-making that it's as interesting, if not more so, as a dungeon I'd hand make, and figuring out explanations for weird combinations is fun. It's also very relaxing; just the right mix of input and output to make me totally lose track of time.