http://www.ala.org/united/United for Libraries: Association of Library Trustees, Advocates, Friends and Foundations
On February 1, 2009, Friends of Libraries U.S.A. (FOLUSA) and the Association for Library Trustees and Advocates (ALTA) joined forces to become an expanded division of ALA known as the Association of Library Trustees, Advocates, Friends and Foundations. Resources for Friends section has a number of useful fact sheets and tool kits on organizing and managing a Friends group.
From Wisconsin's handbook for public library trustees, an overview of the role of Friends, how to develop a good relationship between the library board and support groups, and financial support from the Friends.
To foster improved abilities on the part of library trustees, Friends & advocates, in order to create better libraries and library services in Wisconsin.
Designed to help new non-profit organizations complete IRS Form 1023, the Application for Exempt Status Under Section 501(c)(3) of the Internal Revenue Code. Be sure to take a look at the FAQ.
One of the Fact Sheets at United for Libraries.
Another fine example of a Friends page. Particularly noteworthy is the way in which the site integrates information about the Friends and the library.