The Creation Kit offers the same suite of tools that Bethesda Game Studios used to create The Elder Scrolls V: Skyrim and will be a free download via Steam. The Creation Kit has lots of new features, including the ability to build archives. Plus you'll want to check out the Creation Kit Wiki, our online documentation and help file, for more details.
With Skyrim Workshop, you can browse and search for the latest or highest rated mods, subscribe to any that interest you, rate your favorites and post feedback. Once you've subscribed to some mods, start the Skyrim launcher and you'll see your subscribed mods automatically download. The launcher will even check if a mod has been updated and grab the latest version.