RFCUtil 
Perl script allowing access to RFCs by number and full-text search of all documents. It features command line switches to spawn lynx or w3m to view the RFC, dump to file for offline viewing, or mailing to an address.
http://www.dewn.com/rfc/RFC-Editor
Contains RFC news, search feature, details of the RFC-Online Project, and ASCII and PDF versions of all documents.
http://www.rfc-editor.org/
RFC Viewer
An RFC browsing utility for networking program and protocol developers.
http://www.effetech.com/rfc/
RFC Search
A search engine for locating RFC's and Internet-Drafts.
http://mirror.switch.ch/cgi-bin/search/nph-findstd/
RFC Ref
Repository of RFC's in hyperlinked, colorful HTML format; table of contents appears in separate frame.
http://www.rfc-ref.org/
