I was searching around the net and found these mods over at Strategy Informer. Most of them tweak the game in some way, but there are a few adventures available. I haven't tried any, but after I get done playing Dragon Age and the rest of the games that will be available out this holiday season, I'll give these a go.
There isn't the kind of mod scene enjoyed by NWN 1 and 2, but there are a few modders out there making adventures for The Witcher.
-- Despite all my rage.
I'm still just a rat in a cage.