I would love to donate bandwidth/storage. I haven't a clue how. I wish there was software I could throw in my server, set how much storage and bandwidth I can donate and run 24/7.
Semi-unrelated, but if you're looking for ways to help and have a spare server, Archive Team [1] is always looking for additional capacity. Although Archive Team != archive.org, they do grabs of at-risk content which (almost always) get uploaded to archive.org. [disclaimer: I help out with various Archive Team projects, the most recent of which was the backup of Yahoo Groups).