RFC Editor (Popularity: )
http://www.rfc-editor.org/ Collates Request For Comments documents. Explains the RFC process, and includes a searchable database of RFCs.
Protocols.com (Popularity: )
http://www.protocols.com/ Features an overview of various networking and mobile communications protocols, white papers, and links of interest.
The Kermit Project (Popularity: )
http://www.kermit-project.org/ A protocol that transfers text and binary files without errors between diverse types of computers over potentially hostile communication links, ...