If you're looking for Steam game giveaways or contests you can try going to www.steamgamesales.com or www.steamcontests.com. Both sites have a great, friendly community that gives away games out of generosity every few days.
You can also try looking on Cheap Ass Gamer or the gaming section of Reddit if you want to find a game giveaway/contest for any other type of gaming giveaway/contest.