That's right ladies and gentlemen, the Unreal Tournament III beta/demo is out (today) as well as the Call of Duty 4 demo (yesterday).
They are available on sites such as
FilePlanet, and probably elsewhere.
Grab them and come frag online!
P.S. : I have no idea whether the COD 4 demo offers singleplayer or multiplayer. Although the UT III beta/demo offers both online play or local play against bots.