omCollab is an open source project combining wiki, blogs, social bookmarking and addtional optional applications under a common integrated skin with single sign-on capabilities. See http://mike2.openmethodology.org for current implementation example.
QuickSSO is a powerful and easy-to-configure cross-domain Single-Sign-On solution. The server is implemented by J2EE, but it does not restrict your develop language. You can add your application to SSO not only B/S application but also C/S one.