Okay, I fucking love D&D. I think it's one of the greatest games ever made. The fact that the rules are very open to modification and change (in 3e & 3.5e, at least, those are the only ones I've played) makes it fun as a player or a DM.
Right now, I'm DMing one game. We play it weekly after school, and my group is about 4-5 people. It's really interesting to see how different people enjoy the game. Like, two of my players really love character development, one of them likes exploring, one of them likes everything, and one of them loves combat. Balancing the parts so that everyone has fun is a challenge and very cool.
am bored of the setting
My school game uses a Steampunk Oriental setting. The core D&D setting is very bland, I find. Not in terms of variation of creatures, but more in that it's very cliché. It's been interesting to spice things up a bit more. I've been creating the ghosts in this campaign by using both the Ghost and Zombie template, which has resulted in some interesting battles. Plus I got rid of the normal leveling system and am rewarding levels for character development and impressive feats. For example, our "druid" character (not really a druid but I can't remember the name) levels up by absorbing ectoplasm from ghosts he defeats, and then he gets some of their memories. And of course, we've had some airship battles, which have been fun.
I was also recently playing in a very epic (in length) game. We started at level 7, but I was late to the game so I got in while they were level 9. When we left off we were fighting ant-people on the lawful neutral plane, at level 18. I think the game has lasted about 2 years so far. My character is/was a monk, and I have to say it's my favorite class. (Even though it's very 5th-y, like a Bard, in that they're hard to include in a 4-man party.) Unfortunately our DM doesn't have enough time to plan things, which brings me to...
where the DM just made stuff up on the spot
When I DM, I think up very little ahead of time. Most of my games are spontaneous or chosen from a list of ideas. Like I have a list of possible adventures for my Steampunk Oriental campaign, and then whenever we finish one I just roll to see what we do next. So, since my DM doesn't have time to plan for his Epic Quest, I'm taking it over. So that's a second game I'll be running. Currently its setting is in the other planes, so that's a nice change from the standard setting.
And I am planning to start up a family game of D&D, soon. My mom doesn't like combat so she'll want to be a bard. I'm thinking the setting will just be the standard D&D one, because I can't think of any others that they'd really like. But that should be interesting.
I really need to find a group to play in, though. As much as I like DMing, I really love being a player. I've got the AD&D core books and a bunch of adventure modules which I picked up second-hand, and I'd really love to use them some time. Or maybe a Pathfinder game, because it looks pretty cool from what I've seen of it, and monks become even more awesome. :D