Well, I'm currently running Keep on the Shadowfell--despite disliking what I've seen of 4E, I felt compelled to give it a fair shot in play. Our first session went alright, but not great. The emphasis on tactical miniatures-based combat is a little bit much for me--sort of the opposite direction that I would like D&D to move in, personally. I prefer combat to be faster and more narrative and imagination-based. I have other gripes as well, but I won't go into them here. That said, I'm looking at both C&C and OSRIC/1E as alternatives. Labyrinth Lord/Basic D&D looks interesting and quite well-done as well (I started with the Classic D&D boxed set [1994]) but I like having the full range of race/class combinations available.
That's about it for D&D or D&D-like. Other than that, I have Spirit of the Century and have been wanting to play it. Actually, there's a whole list of other RPGs I've been wanting to try: Call of Cthulhu, Trail of Cthulhu, Sorcerer, The Riddle of Steel, Ars Magica, WHFRP, Runequest... the list goes on.