If you're just itching to play the HL2 sequel the very moment that it's released, you can get your pre-load groove on, starting now.

"Half-Life 2: Episode One, the first in series of episodic games from Valve, is now available for pre-purchase and pre-load via Steam. Those who pre-order the game before it is made available on June 1st will save 10% off the $19.95 price."