Been a while since I've done one of these, but finally the workshop's out and the modding has picked up a bit.

Sounds Of Skyrim: Dungeons by Cliffworms http://steamcommunity.com/sharedfiles/filedetails/?id=9106

This is a great mod that adds a bunch of sounds to a variety of dungeons to really pump up the immersion, from rats squeaking to wooden frames creaking. 5 stars!

Sounds Of Skyrim: Wilds by Cliffworms http://steamcommunity.com/sharedfiles/filedetails/?id=13231

Part of the same project, this mod adds a ton of immersion to the wilds of Skyrim, including the sounds of bats flying and the howls of wolves in the night.

Fall Of The Space Core, Vol. 1 by Valve http://steamcommunity.com/sharedfiles/filedetails/?id=7375

You don't need me to tell you what this is.

Dwarf Race by Jerry60k http://steamcommunity.com/sharedfiles/filedetails/?id=12061

HOLY SHIT, PLAYABLE DWARVES. Jerry60k is my new god for making this. Arms are a little weird and kill animations are broken, but DORFS!

If you want to check these out, here's a video: