We offer free booth space to game developers at the conventions, but it takes a little different shape depending on where you go: PAX 10 was the original "indie" showcase, at East it's similar but focuses on mobile, and the newest show in San Antonio focuses exclusively on tabletop offerings.
And what a crop this year! Good lord. Don't forget to check some of the official sites: a couple of these games already have Print & Play options, so you don't even have to wait.
(CW)TB