Reddit, a fairly popular online forum/community, is offering $100 in ad credit to nonprofits. They have message boards covering most imaginable topics, including many cycling-related boards (go to http://www.reddit.com/r/bicycling, see list on the right side) and boards for most cities. I'm pretty sure you can set your ads to run on the boards of your choice.
It might be helpful if you're looking for a few small donations or more Facebook likes or general buzz for your org. It doesn't explicitly mention that 501(c)(3) status is required to sign up, either.
Here's the info: http://blog.reddit.com/2011/09/if-youre-nonprofit-organization-we-have_14.ht...
Thank you!
Ryan Feller, Director Bike Broward (954) 232-3790 www.bikebroward.org ryan@bikebroward.org