hmm...scheduling can become very hard, very quickly. what operating system would you want the software for? windows? linux? MacOS?

doing a quick search on http://freshmeat.net/ i came up with some possibilities...first, there's the project-management types of programs (similar to Microsoft Project, if you've ever seen that). and then there's this one:
http://freshmeat.net/projects/yellowtip_health_reservations/
it seems that it costs money, but they have a free demo.

It might also be possible (and maybe easier/cheaper) to do it by hand, once you've learned some extra strategies. Things like assigning the most-constrained one first....like if you have students and class times and one of the students has only 2 times she's available, while another student has 5 times she's available, try to schedule the 2-time student first because she'll be harder to squeeze in there later once a bunch of spots are taken up. she's more constrained, so you have to accomidate her early to make it easier. if you wait until later, then maybe no spots will match and you'll have to backtrack

i'm not sure how clear this is...i used to write computer programs that do this, but they were all written specifically for a certain job (like scheduling football games into stadiums, etc). what i'm saying might make sense to me, and not to anyone else ;)

With a little practice, and maybe some pieces of paper cut out so you can rearrange them by hand, you could probably learn to do it yourself. The NFL schedule is complex enough that it is really challenging for computers to find a schedule that fits, but the way they've done it for years is they have this 75-year-old guy with a big board with little hooks on it. he has a piece of cardboard representing each team and a hook on the board representing each stadium-time that's available, and he just hangs them up there and rearranges them by hand. he's figured out a lot of little tricks over the years. the point here is that your situation is simpler than the NFL thing, so in theory it's possible to do it by hand, but it might still take some practice before you get good at it.

the thing that worries me about software is that it might take some set-up time before it is able to schedule your situation...but i'm not sure. maybe give that demo a try and see how it goes.

hope that helps....sorry if i'm too vague

-doviende