Here's a summary of the competitions which developers can participate in and win some money:

Gaming World ($450, 2 weeks)
The easiest of the lot. Make a game in two weeks, and stand a chance to win USD $300. All development tools are accepted, but creation must include pandas (among other rules). Final submission date is 28th of April. First and second runner ups get USD $100 and $50 respectively. (forums)

Eegra 1st Annual Game Making Shinding (USD $2,500, 3 months)
Eegra is offering cash prizes worth a total of AUD $2,750 (roughly USD $2,500) for first to third place finishers in their 1st Annual Game Makin' Shindig Competition. Contest runs for three months, with 8th of July set as the final submission date. Entrants are advised to read the Terms and Conditions plus Guidelines for Entry before considering participation.

The Dobbs Challenge (USD $10,000, 2 months)
Microsoft is giving away USD $10,000 just for modifying games using the trial version of Visual Studio 2008. That's a lot of money for a couple of weeks' coding.

10 Indie, Student Game Competitions
A list of ten indie and student game competitions that would interest developers who are keen on getting a little attention for their projects or releases.

The rundown (unranked) points to ten events throughout the world in which indie game developers and students can show their works to compete for cash prizes, as well as that first big break in the industry.