There will be a number of significant Steam events in the coming days.
The first will be a long-awaited Steam client release. The highlights from this release will be:
Account validation (via e-mail)
A new Half-Life 2 hardware survey
Support for purchasing games through Steam
There are a number of other small changes along with the ones listed above, as well as a number of changes planned out past the launch of Counter-Strike: Condition Zero.