Iris2
We haven't typed a word about Iris2 in over two years! There are quite some new bugfixes to the 3D UO client.
The latest stable release (rev 3395) is one week old.
Iris2 was updated to use Ogre 1.7.2, it now runs stable on Windows.
This old video is still pretty much up-to date
The project mainly suffers from lack of community interest and aid in creating or converting free assets or hosting servers. :) A few trees seem to be hard enough (but there's more).
RunUO appears to be a popular server suite.
I made a feed of the Iris2 wiki news.