As the thread title says, what mods are you excited for? Tell us the name of the mod, what game it's for, a synopsis, and a link to their page.

I, myself, am looking forward to Outbreak: Condemned for Half Life 2 (Even though I won't be able to run it). It's a Resident Evil mod, that's looking pretty damn good so far.
Checky!

Also I'm intrigued by Catalyst. It's going to be a alternate sequel to Half Life where it crosses over with Quake 2. I figure it's either going to be amazing, or suck harder than a black hole, and either way, I think I'll try it out.

So what are you excited for?

Black Mesa for any Source game that comes with the SDK.
A total conversion remake from scratch of Half-Life in the Source engine.

Dear Esther, not sure yet if you need a specific HL (source) game to run it.
A thoughtful experience from beginning to end, it's about exploration of an Island and at the same time exploration of yourself. It takes the S out of FPS.
A graphic overhaul is in the works right now done by a very talented level designer that already worked on commercial titles.

Zeitgeist, not sure yet if you need a specific HL (source) game to run it.
What if the 1st World War didn't turn out the way we know it did? This mod tries to crate a unique style and setting in a dystopian 1930... sounds intriguing.
Here's a draft of what they are trying to achieve.

S.T.A.L.K.E.R. - Lost Alpha for S.T.A.L.K.E.R. - Shadow of Chernobyl.
The way S.T.A.L.K.E.R. should have turned out?

Call of Pripyat Complete for S.T.A.L.K.E.R. - Call of Pripyat.
Another Complete Mod. I suspect it will make the game even more awesome.

Raindrop for OGRE engine now it seems (was a source mod before but now I guess it qualifies for Indie).
The setting is reminiscent of S.T.A.L.K.E.R. but with a twist... :P

HL2 Wars for HL2 Episode 2.
Ever wanted to play Half-Life themed RTS game?

Those are the ones I can think of from the top of my head right now but there are many more I'm looking forward to.

The Dark Mod

Open Outcast, Dear Esther, Call of Pripyat Complete and Zeitgeist.