There's an in-development game at the tigsource forums I thought some of you might be interested in.
It's a platformer, not a roguelike, but it has a few roguelike aspects such as a randomly generated play area and character levelling.
Basically you're this little guy descending into a dark, monster-filled abyss. In addition to the monsters that must be either fought off or avoided, you will also be threatened by the abyss itself, with deadly spikes, perilous drops, and an eternally falling screen threatening to crush you.
To help you survive, you can gain a wide variety of unique and interesting abilities from experience dropped by enemies. These include things like double jumping, teleportation, fist upgrades that let you do more damage or punch through walls, and various upgrades to your ranged "star" attack.
The game doesn't have an ending - the challenge is to see how deep you can go, how high of a score you can get, or how powerful you can make your character.
If any of that sounds like your type of thing, check it out
here.
PS: The fluctuating "probability" numbers are your health. If they're hovering around the single and double digits, that means you only have 1 or 2 hits left.
My record is
2.079 3.276 km. See if you can beat it!