(see specifics after the jump)
The first place I looked was Craigslist, where I found an owner of a pony stable who offered free manure for anyone willing to come and get it. They left a phone number in their ad, so I took that down and will call them at a more appropriate time of day. Basically, trolling craigslist consists of first going to my local craigslist, then scrolling to the "free" section of the "for sale" column. Not content with just checking there, I also went to the "farm & garden" section and looked for horse stables offering space. I e-mailed these posters and asked if they would be willing to part with some of their manure. Hopefully a few will respond, but I figure it can't hurt.
Next, I wandered over to freecycle. It's a network of people who offer things to share for free, where you can post a WANTED ad or an OFFER ad. It's fairly restricted and they discourage want ads until you've posted offers, but I joined last year and posted an offer of teaching supplies so I should be ok. Freecycle requires a membership, and the individual communities are only as friendly as their moderators. Ours is less welcoming than others I've joined, but it's not terrible. I posted a wanted ad for soil or manure, and it's waiting confirmation by the moderator. We'll see if it bears fruit.
State Dept of Environmental Protection (http://www.ct.gov/dep/cwp/view.asp?A=2718&Q=325352)
My state requires cities to recycle leaves, and many cities allow residents to take small amounts of the compost created by recycling. Unfortunately, tracking down the municipal composting companies is difficult. I suspect this is because their first priority is getting the leaves composted, their second is using it, and customer/citizen services is a distant third. However, I eventually found a list of all of the city composting plants in Connecticut at http://www.ct.gov/dep/cwp/view.asp?A=2718&Q=325374. So, I'll give them a call and perhaps get some compost for free.
So far that's it. I wish there were more.