There’s a list of SXSW Interactive panels by category here:
http://2008.sxsw.com/interactive/programming/panels_by_category/
Most of the people who come to Austin for the Interactive Festival are in an “interactive” business, however you want to define that. Web developers, social networkers, designers, bloggers, animators, entrepreneurs, etc. People come from all over the world, but it’s an urban, relatively young crowd—with an occasional grayhead like me.
The previous comment about the music part of the festival doesn’t really apply to the Interactive Festival because they don’t overlap. The Interactive Festival is crowded at the Convention Center, and a few panels get close to full, but the city in general is not affected much by the Interactive Festival, the way it is by the music portion of SXSW, which starts the day after the Interactive Festival ends.
There’s also a film part of SXSW, which does overlap with the Interactive Festival, and the past couple of years there has been a new game section too, called ScreenBurn.
It’s a fun event, and the Ellis Labs party was great this past year.