There's a great collection of podcasts here: http://hackermedia.org/ and here: http://www.thelinuxlink.net/

The 2600 family of shows: http://www.2600.com/offthehook, http://www.2600.com/offthewall and the Hackers On Planet Earth conference archives: http://blip.tv/2600magazine/rss

Security now: http://twit.tv/sn

This Developer's Life: http://thisdeveloperslife.com/

The Linux Action Show: http://www.jupiterbroadcasting.com/show/linuxactionshow/

Techsnap: http://www.jupiterbroadcasting.com/show/techsnap/

Ubuntu-UK Podcast: http://podcast.ubuntu-uk.org/

Free As In Freedom (The Software Freedom Law Show): http://www.softwarefreedom.org/podcast/