Kindista.org is an online tool for the sharing economy, and in many ways it is the online version of gift circles. Sign up and list things you wish to offer or receive.
The ultimate book on gift economy, and why it is important in our world is Sacred Economics by Charles Eisenstein. You can read it online, only paying what you choose (gift economy!) at http://www.realitysandwich.com/homepage_sacred_economics. Chapter 18 talks about gift circles.
Shareable.net is a leading resource on the sharing economy, of which the gift economy is one sector. They publish an excellent website and newsletter, also research reports, bookstore, and more. See, for example, this article on their site about gift circles in Berkeley.
For a bunch more links, take a look at the Gift Economy page on Tree Bressen’s website.