In choosing to buy my GenCon pass via the Forge, I painted myself into sort of a corner, as GenCon hotels are only available via the registration site.
However, I found a really cool hotel that's basically across the street from the convention center, a Best Western that hasn't even opened yet (opens next month). Rooms are $135 a night.
Check out this page for info: http://www.dorabros.com/BestWestern_Indpls/BestWestern_Indpls.htm
-Matt