There are notably more contests than usual now and many are listed in our contest section. Prizes and acclaim are meant to attract great developers to build cool things on top of each company's API. Some of these challenges end soon, so you'd better get started.
Producteev's Developer Throwdown (above) encourages coders to integrate with its web-based task management system. Ideas include desktop versions, mobile apps, and plugins for browsers or Outlook. Producteev is giving away as much as $2,500 and the contest ends August 15.
Apps for Californians is an open government initiative (which we helped launch) to leverage public data sets. The data is specific to California, but the contest is open to anyone in the U.S. and ends August 27.
Constant Contact Developer Challenge is pushing email newsletter-related apps in three categories: Social Media, Mobile and Contact Management. Winners in each category receive $5,000, $2,500 or an iPad. Best in show takes home $10,000.