According to Gamespot, Team Fortress 2 now sports a cartoonish art style and a 60's spy feel akin to that of Monolith's No One Lives Forever -- certainly a description you'd never expect to be about a game from Valve. The developer is also trying new things with Portal, which incorporates a rather imaginative gun and encourages you to blast Prey-like portals into floors and walls for all manner of object shifting, puzzle solving hijinx.
The console versions of Half-Life 2 (along with all the extra goodies) are expected to launch alongside the PC game's second episodic expansion. Barring unforeseen code thefts and other delays, that means they'll be out by the end of the year.
[Thanks Easy_G and icemorebutts!]