For the owners of Counter-strike: Condition Zero (CS:CZ) (highly recommended) and ATI video cards with the voucher for a free copy of Half-life 2, Counter-strike: Source is available for preloading through Steam.
If you own a copy of CS:CZ (or are going to buy one), make sure you register it in your list of games. You need to click “Browse Games”, then click “ Register a product I already own”. CS:CZ should show up. A bit later the Coming Soon section will appear, allowing you to download the 2.0 GB to your machine ahead of time. On the 18th of August (tomorrow) the beta of Counter-strike: Source (aka CS2) will go into beta for you. It looks very promising.