Kotaku has a video featuring a preview of Skyrim's creation kit and its integration with the Steam Workshop.
The mod tools are pretty neat, but not being a modder myself, they just look like mod tools to me. The Workshop integration, on the other hand, is one of the best things that's ever happened to modding. It makes it so ridiculously easy to share, find, and install mods that I can't believe no one's ever done anything like this before. Seriously, it's awesome. No worrying about install directories or downloads, it'll do all that itself. And presumably, considering Bethesda's launcher style, you'll be able to easily activate and deactivate mods that you've downloaded.
Also, for some reason whenever I type Bethesda my fingers want to throw a 'y' on the end there. Not sure what's up with that.