This is an ongoing project to keep a fresh and working list of free tv sources. Please share a link to this page, because the more people that visit it, the more time I can devote to keeping it updated.
Updated September 13, 2009.
Added Hulu and Crackle!
Updated August 01, 2008.

All links require no registration and were screened to be legal! Here's the list!
Please inform me if you find illegal content.


Crackle - Full Movies and Series

HULU - Full Movies and Series Here Too

Fox

ABC

NBC

AMC TV (Potential popups here)

Big Ten Network (Sports clips)

Biography

Discovery Channel

Discovery Health

Discovery Science

Military Channel

History Channel

Indipendant Film Channel

Music Television (MTV)

Life Skool (New and content filled like a jelly Donut!)

National Geographic

National Lampoon

SPEED (NASCAR)

The Learning Channel

Thirty Mile Zone (Celebrities)

Travel Channel

TVLand

Weather

UKTV

The Suite Spot

UKTV

Sky

If those commercial suppliers don't suit your desires there is a wealth of websites which provide video, but often of less quality.
(Review: Generally riddled with static advertisements, but huge selection - I did a quick scan for pop-ups and found none to mention and no viruses. If you find any please email me and I'll remove them from this list.)

http://wwitv.com/portal.htm
http://freetube.110mb.com/ (Good interface, little ads)
http://www.channelking.com/

Websites offering only teaser-ish videos (usually only clips less than 3 mins long: A&E, AMC, Fuse, Fuel, HBO,
http://www.liveinternettv.net/
http://www.yourglobaltv.net/ (Huge free movies selection)
ViewMy (Very nice interface, not riddled with ads)

Common Plugins required to watch these channels (in order by most likely to be used)
Flash Player
Windows Media Player
RealPlayer
Quicktime
Winamp
Divx Web Player

Don't forget to help keep barbed wires off of the internet!