Doom II levels
I work here. There is a bit of overlap between what we do at the office and what I release on my homepage, so check it out if you like my stuff!
The makers of the Iji soundtrack.
Speed Demos Archive
Speedruns of games new and old.
Tool-assisted (not realtime) speedruns of even more games new and old. Note that these are a completely different kind of movies than those in the link above.
Free remixed video game music.