Lightroom-like software for video (categorizing & organizing footage) I use Lightroom's library system to organize my photos using tags and categories. Now I want to have the same functionality for video footage, especially for extracting and organizing the interesting sections of a clip.

Is there something like that, maybe even as an addon for lightroom?

Cheers,
fabs
I think the keywords your looking for is "media asset management" or "video asset management". Apart from the numerous commercial softwares around, this list of open source alternatives might give you a good overview. 

http://www.opensourcedigitalassetmanagement.org