From BBC Persian, protesters throw tear gas cannisters back at police then send them running. Raw:

Video

Ten other "significant" Iran videos via Boing Boing

Added but extremely graphic:
If you have the stomach for it — and DO NOT click there if you aren't ready for blood and dying — here's YouTube video of a girl being killed on the street while relatives wail. The video came with a message: "The film is shot by my friend who was standing beside me. Please let the world know." The so-called "Neda" video has become a big thing globally, says CNN. Robin Wright, the Iran expert formerly at the L.A. Times, writes at Time.com: "Although it is not yet clear who shot 'Neda'...her death may have changed everything."

Video via Boing Boing and Andrew Sullivan