The Rockstar Hits Collection is also on sale for $29.99. It's a Steam bundle that includes GTA IV and its Episodes from Liberty City expansion, Max Payne 3, and LA Noire. Pretty much every other Rockstar game on Steam right now is also on sale to varying degrees.
Recent PC arrival Brutal Legend joins the salesapalooza by slashing its price in half, down to $10 for the weekend starting now; if you want to pick up the soundtrack with the game, that'll be $12.49. Creator Tim Schafer of Double Fine Productions has stated he would "love" to revisit the game and add more stuff if the PC version does well.