CelebrateFriendship.org 
A historical, political, and cross-cultural perspective, with a bibliography and links to other resources.
Friendship
Ladies' Home Journal Online's "Friendship" category, with advice and other links relating primarily to women's friendship.
Friendship - Suite101.com
Collection of articles, references, links, and discussion lists about friendship.
Friendship Links
A page with links to many different sites about friendship, including poetry, history, and formal research studies.
The Friendship Page
A large site with quotes, poetry, philosophy, humor, links, a chat area, and so forth.
The Magic Of Friendship
Reflections on friendship including definitions, stages, poetry, and a funeral service for a friend.
MyFriendsConnection.com
Friends networking site with ability to meet friends of friends through unlimited levels. Includes photo profiles, connections, birthday reminders, and searches.
Queer Friendship Resources
A site containing links, book reviews, and other information that relates to nonsexual friendships in the gay, lesbian, bisexual and transgender (GLBT) community.
So... Are You Two Together?
An article in Ms. Magazine about a modern-day Boston Marriage (committed living-together friendship) between two straight women, from a first-person perspective.