1. Merchandise: make all kinds of cool stuff related to your film to sell at the fest. T-shirts, buttons, books, all manner of clothing, lunch boxes, and whatever makes sense for your movie.
This, after all, is how George Lucas got rich (through merchandise, not selling them at indie fests though, as far as I know :).
2. DVDs - if the fest is cool with you selling & signing DVDs, that is another way to make some $s.
3. Posters - this would fall under merch, but these you have to make anyway, might as well make a couple hundred extra in case some peeps want to buy them at the fest.
4. movie soundtrack CDs - again, more merch.
5. Set up a DIY screening to follow the fest screening. Right after the fest screening is over (not like the same night, maybe a week or more later), set up a DIY screening. Unlike at the fest, you get to keep all or some of the ticket sales $s from this. And another chance to sell merch. Maybe having played the fest will help lower your publicity costs.
6. Use the fest play & trip to the fest as a scouting trip for future biz opportunities: visit the local indie theaters, say hello to the programmers, tell them that your awesome flick is playing in the local fest & that maybe later they might want to take a look at the movie for a possible booking. visit the local indie record, DVD & other relevant retail folks, get yourself set up for future business dealings with them. same with local press.
7. After the fest, promote the movie through local media & advertise the DVD. Perhaps the fest generated some press that can be used in the promotion, or the fact that the film was selected to the fest may be enough. If locals heard about the film through the fest but missed it, perhaps this will be an opportunity for them to check out the film on DVD/for you to make some cash.
8. I wonder if you can get small business or corporate sponsors for your fest appearance. Hmmm. Like maybe they'll get to advertise on yer site, blog, film promo material like posters & flyers, your clothing or whatever in exchange for them paying you some money. Maybe complicated, but maybe worth looking into.
9. Great fest coverage at your blog: may drive up your number of visitors, and that may help with any affiliate programs & advertising revenue stuff that you may have going on at your blog.
Check out a bunch of films, talk to people at the fest - filmmakers & audiences, load up some photos & video & do the DIY journalist thing.
So I guess the possibly indirect ways to make some money from the fest experiences boil down to: 1. merchandise, 2. getting to know future business partners/collaborators (of course you should follow up later and get the movie into the venues & get sales), 3. post-fest screenings maybe, 4. perhaps some $s through reporting on the fest, and 5. possibly sponsorship/advertising.
Indie filmmaking is time consuming & thus can be expensive, and distribution, at any level, is both time consuming & expensive, so, being on the lookout for cash generating opportunities is a very good idea.
If you've got some ideas to add to this list, post 'em in Comments. Thanks!