Were you able to find a venue for $500? I noticed that someone had suggested having a wedding on a weekday to save money.
If you were able to move your wedding up & get married on a weekday (Monday - Thursday night) by August, 2011, you would be in the $500 range at the Caswell House with the special that they're offering. You would need to use one of their preferred caterers too to get $200 back to get you at the $500 point.
I had been to a friend's wedding at Lakeside Pavillion in Marble Falls -- it's a pretty venue located about an hour out of Austin. They do have an opening for Nov. 26 & Dec. 24 & 31 there. Their fee is $500.