Weekends are the perfect time to get in a bit of PC gaming and if you're looking for something to throw your mouse and keyboard at, Green Man Gaming is offering 25 per cent off all titles until July 9, including those already discounted.
As per this blog post on the retailer's site, all you have to do is enter the code "25OFF-ALLTH-EGAME" when purchasing a game. It's good for an unlimited number of uses, as long as you get your shopping done within the next few days. According to OzBargin, the code should be good until 9PM Monday. Having given it a test, the code also works on titles already on sale.
My personal recommendation is Endless Space, a great 4X title that, with the code, you can grab for around $US26.
Note the code must be entered in all caps, otherwise it won't work.