Zero-K is the reboot of Spring RTS game Complete Annihilation, with aims to distance itself from the TA IP that has plagued Spring games, and just generally be better in every way :)
It comes with a revamped UI, multiple specialist commander units to play as, and a single faction instead of the traditional 2. The team is also providing a set of web services such as map and mission lists to enhance the experience, and maybe we'll even see the resurgence of Planet Wars, the awesome persistent galactic RTS that was running a while back
IrrRPG Builder looks like a promising 3D RPG IDE. So far, it features a terrain editor, drag and drop object placement, and scriptable using Lua.
There's a set of tutorials to get you started, and comes with enough content to play around with; the scriptable object system along with template scripts make it really beginner friendly. The built-in script validator could use a bit of work (doesn't detect undefined functions yet, which crashes the game) and adding some sort of api refference along with autocompletion would really make it a fully fledged IDE :)
We've been giving Ryzom quite a bit of love recently, with their Linux native client and all, but they just announced an In-game competition for a Linux netbook and got accepted for the Google Code-In initiative. Here's hoping they have lots of success!
Warlock's Gauntlet is a highly polished Gauntlet/Diablo/Hack'nSlash mashup. A nice interface, smooth gameplay and lots of spells make this a very nice find.(Thanks archl from the comments :) It even has co-op!
The Egoboo team just released their version 2.8.1 beta, it adds randomized loot, special effects and lots of bugfixes. Check it out!
Freedroid recently had their website redesigned(aww I liked the old one :(), and also released version 0.14 which included the Summer of Code work. This added better randomized dungeons, a better interface for the level editor and replaced magical weapons with a more sci-fi addon system (the last addition was done by Nekotaku from Lips of Suna, which also had a release recently :)