Request For Comments
Internet Standards, Information, Best Common Practises, and other related stuff. Heavy reading, but if you want to know how the Internet works, there is no other way.
Also has some humorous ones, like HTCPCP.
Of particular interest is the Best Current Practice sub series: BCP
Wiki handles RFC's, to refer to an RFC type RFC:1918
RFC is an Acronym
9 pages link to RFC: