I just started to play
Enderal, a total conversion of Skyrim that basically turns it into a different game, complete with a new map and a new level system based on experience points.
Looks very interesting and seems to have a significantly darker story than Skyrim.
The German version came out today and is unfortunately still prone to crashes between areas and cutscenes. Frequent saving is recommended.
An English version will come out in late July, but before that there's going to be an option to play with German sound and English subtitles.