Good news, fans of ... well, fans of monkeys trapped in hamster balls who are forced to roll through perilous obstacle courses in a sad attempt to collect bananas. Sega recently announced a halving of the price for Super Monkey Ball 2 on the iPhone, which reduces the cost to a mere $4.99. If you've been waiting to fulfill your spherical, simian desires, this might just be your best chance.
If rollin' monkeys isn't your thing, check out Touch Arcade for a pretty sizable list of temporarily discounted apps. They'll cater to a much broader range of interests, including poker and zombie pizza-making.