Funny you should ask that question. Firstly, check w/ friends w/ aquariums. You can always make some friends happy, esp if you have a quality spawn.
Next contact your LFS, find out if they'll buy or extend credit for fishies.
If all else fails, everyone talks about aquabid, seems like a good idea.
Personally, our LFS has already agreed to take on all fry that we want rid of in exchange for credit, gotta love that, fishies for fishies. *celebratesmiley*