Extra Adventures for Castle Ravenloft
BoardGameGeek Castle RavenLoft has quite a few used-made scenarios and extra characters.

The most are listed in the Variants forum, although you may look around in there a bit and find some others under "rules" maybe.

One of my favorites is "Crypts And Creepers", although it's more of an 'expansion', not just another scenario.

WotC is also having a "Build your own scenario" competition, so you should see more available on-line when that happens also.

Here's a link I just found that has most of the user-created adventures listed and ranked:

BGG Castle RavenLoft Adventure Database