Many specifications for the Internet are published as so-called "requests for comments" or "Internet drafts". They can be browsed and searched via www.rfc-editor.org and www.ietf.org. I've collected some RFCs here in the hope that you need not search as long as I did. :-)

If the link to a draft on the IETF server doesn't work any longer, it often helps to increment the draft number in the URI once or twice and retry; old versions of draft documents are removed from the server.

HTTP

HTTP/1.0 protocol: RFC1945
HTTP/1.1 protocol: RFC2616 (errata)
HTTP version numbering: RFC2145
HTTP authentication: RFC2617
HTTP extension framework: RFC2774
HTTP state management mechanism ("cookies"): RFC2965 (practice: RFC2964)

FTP

FTP: RFC959
FTP security extensions (the commands "AUTH", "PROT" etc.): RFC2228
FTP extension for IPv6 and NATs (the commands "EPRT" and "EPSV"): RFC2428
FTP security considerations ("bounce attack" with proxies; password guessing): RFC2577
Firewall-friendly FTP: RFC1579
Anonymous FTP: RFC1635
FTP feature negotiation (the commands "FEAT" and "OPTS"): RFC2389
FTP i18n: RFC2640
FTP extensions (draft #16, expired March 2003; the commands "MLSD", "MLST", "SIZE" etc.)

Mail and News

Internet Message Format: RFC2822 (Usenet: RFC1036)
SMTP: RFC2821
Message Submission: RFC2476
POP3: RFC1939 (extensions: RFC2449; response codes: RFC3206; scheme: RFC2384)
IMAP4: RFC3501 (obsoletes RFC2060; implementation recommendations: RFC2683; scheme: RFC2192; extension drafts)
AUTH extension for IMAP/POP: RFC2195
NNTP: RFC977; replacement (draft #25, expires August 14, 2005); extensions: RFC2980; scheme extension draft
Read This Before You Write a Newsreader

TLS/SSL

TLS 1.0: RFC2246 (version 1.1 draft #9, expires June 2005)
TLS extensions: RFC3546
TLS compression methods: RFC3749
HTTP over TLS: RFC2818
HTTP/1.1 upgrade to TLS: RFC2817
Securing FTP with TLS (draft #16, expires 13th August, 2005; information)
Using TLS with NNTP (draft #4, expires July 2005)
TLS with IMAP/POP: RFC2595
SMTP over TLS: RFC3207
HMAC hashing: RFC2104
SSL 3.0 (draft #2; an analysis)

Miscellaneous

Requirements for Internet hosts: RFC1123 (updated by RFC1349 and RFC2181)
Security Mechanisms for the Internet: RFC3631
Security Considerations: RFC3552
URIs: RFC3986 (updates/obsoletes RFC2396, RFC1738 and RFC1808; report: RFC3305; schemes: IANA, W3C)
Base64 encoding: RFC3548, 3.
MD5: RFC1321
UTF-8: RFC3629
Finger: RFC1288
Gopher: RFC1436 (URI: RFC1738; tools/groups: RFC1689; Gopher+)
CGI (Common Gateway Interface): RFC3875; W3C
HTML 4.01 (errata)
JavaScript (experimental proposal 2.0)
IPv6: RFC2460; addressing: RFC3513 (obsoletes RFC2373); basic socket interface extensions: RFC3493 (obsoletes RFC2553, which obsoletes RFC2133); advanced API: RFC3542 (obsoletes RFC2292); application transition: RFC4038
IRC: RFC2810 (client protocol: RFC2812)
Internet authentication: RFC1704
Internet Users' Glossary: RFC1983
The Twelve Networking Truths: RFC1925
RFC errata
IETF announcements
User Agent Accessibility Guidelines