I'm created a small website/widget that does the math for an Iowa precinct caucus, in case you're curious to play with the numbers. It's up at http://caucusmath.com. You can play with the numbers to your heart's delight, and see how this mildly crazy system works. When we get results next Thursday, they'll be delegate counts, not raw votes, so understanding how they relate to each other is instructive.
Various candidates (Obama I'm sure, and likely others) have put calculators up as part of their sites for training caucus-goers, but they're all Flash and part of their sites, so not easily accessible (or friendly for supporters of other candidates).
desmoinesdem has a great series of diaries at MyDD about how the caucuses work, especially in the larger context, but I wasn't able to find a good, fast, web-accessible calculator to play with the numbers.
Also, at http://caucusmath.com/... I've made a mobile-phone-browser friendly version (I think -- I only have my phone to test it on), in case you're in your caucus next Thursday and want to run the numbers on your phone. :) (How many do we have to get from the supporters of non-viable candidate X to add a delegate for candidate Y?)
Along those lines: if you have a mobile phone and a data plan, could you check it out and see if it works and looks OK for you? Leave a note in the comments to let me know if it works (especially if something goes or looks wrong).
Enjoy!