CEVO (Cyber Evolution) just announced their tournament, CEVO DotA Season 1. This season features a prize pool of $500 split into several divisions, as the event will consist of two skill divisions, FREE (CEVO-FREE), and Professional (CEVO-P).
In the professional division there will be an entry fee of $5 USD per player. But as an amateur you can play for free, and the sign ups are open now for everyone.
Links
cevo.com - DotA Season 1