I saw an email on the cool ECF charity forum about sources of free/low budget stock footage. Here are the places I've been using recently
Firstly http://www.videvo.net/ and Beachfront B-Roll. They aren't comprehensive at all but if you dig around, and think poetically, there is some lovely stuff. Mixture of public domain and creative commons.
If you can find a bit of money and need a volume of decent stock footage I'd seriously consider Videoblocks. They emailed me a link with an offer for $99 a year. You can access the discount here http://videoblocks.refr.cc/BZ7XKWZ. They have a lot of decent stuff, royalty free and with unlimited downloads. I think they make their money by also licensing premium content you pay extra for. But the archive of subscription stuff is pretty big and if you're going to use 2 clips in a year the $99 kind of pays for itself.
Here's a film about chemsex I made recently and most of the B-Roll and green screen phone footage came from Videoblocks.
Also NASA gives a load of their footage away for free CC use and they have a lot of cool stuff.
There is a lot of video on European Parliament Audiovisual Services for Media, but it's a slightly awkward website and takes a bit of digging - http://audiovisual.europarl.europa.eu/Default.aspx
If you have any other sites and go to places, drop me a note.
Follow @thomhoffman on twitter for more production tips and ramblings.