Here are a number of RFCs in both PDF and text formats.
The Requests for Comments (RFC) document series is a set of technical and organizational notes about the Internet (originally the ARPANET), beginning in 1969. Memos in the RFC series discuss many aspects of computer networking, including protocols, procedures, programs, and concepts, as well as meeting notes, opinions, and sometimes humor.
All of the RFC documents below as well as the rest of the RFC library can be found at http://www.rfc-editor.org/