Well, I was messing around with Steam today as I was preloading Red Orchestra in preparation for the free trial coming tomorrow
. Under the tools tab though was a new entry: Source SDK Base. I don't know what this does, but I downloaded it anyway. Once it was downloaded I ran it and the only thing it seemed to do was run a video stress test using the Lost Coast level.
I don't know if there's more to it than that or not, perhaps you can use the files for this level within Hammer somehow, i'm not sure. I'm sure Valve will let us know sometime, but the way it was just plopped into the list without even a mention is kind of mysterious.
Ah well, I shall wait eagerly until I can play RO.