An excitable post on the Counter-Strike blog announces that Counter-Strike: Global Offensive will be free to everyone from today through until Sunday to celebrate the climax of the Electronic Sports World Cup .
"This weekend? CS:GO is free. Download it. Play it. Love it. It's free. Who knows, we might even put it on sale if you want to keep playing after this weekend," say Valve. They've recently updated their spectator tools with GOTV, an in-game service that should let you check out the pro action happening in Paris this weekend. If you're suitably inspired, you can start climbing the ranks and taking on CS regulars.
If you've never played Counter-Strike before, you won't have to worry too much about running into crack sharpshooters right away. "Ranked players will only meet Free Weekend players skilled enough to climb into their skill group." In the meantime, Valve have put out another Pro Tip video to give you a head start while the client downloads.