Bethesda games (Morrowind onwards) are highly moddable. They basically release the development software with the games to allow users to make changes, quests, locations and more with it. I'm one of these modders.
For Oblivion for example, there are literally thousands of super high quality mods. However, Bethesda usually release the development tools a few days after the game's release. As there are no development tools yet, no mods can really be made. Mods will slowly come out from when the tools are released.
I suggest you check here over the next few weeks

http://www.skyrimnexus.com/