Big Fish Games - 70% off for New Customers (Games from $2.99)
Banner on their web site says one day only, but it's not clear when it finishes.
They have some good games, including Fishdom. The cheapest price I could find on the net, Fishdom 3 Collector's Edition is reduced from USD$19.99 to USD$4.19 if you are a new customer and agree to join their club. (The club is free for the first month, and providing you cancel during the first month there is no charge. If you forget to cancel the club membership, or you want to remain a member, it's $7/month.)
If you buy a Collector's Edition this weekend, you can also get a free keychain.
Just a heads up, avoid Shadow Lake - it's a piece of crap… read the reviews, but there are some games on there that are worth it