Some Important Port Numbers:

Port Number Description
1 TCP Port Service Multiplexer (TCPMUX)

5 Remote Job Entry (RJE)
7 ECHO
18 Message Send Protocol (MSP)
20 FTP -- Data

21 FTP -- Control
22 SSH Remote Login Protocol

23 Telnet

25 Simple Mail Transfer Protocol (SMTP)

29 MSG ICP
37 Time
42 Host Name Server (Nameserv)
43 WhoIs
49 Login Host Protocol (Login)
53 Domain Name System (DNS)

69 Trivial File Transfer Protocol (TFTP)

70 Gopher Services

79 Finger

80 HTTP

103 X.400 Standard

108 SNA Gateway Access Server
109 POP2
110 POP3

115 Simple File Transfer Protocol (SFTP)
118 SQL Services
119 Newsgroup (NNTP)

137 NetBIOS Name Service

139 NetBIOS Datagram Service
143 Interim Mail Access Protocol (IMAP)
150 NetBIOS Session Service
156 SQL Server

161 SNMP

179 Border Gateway Protocol (BGP)

190 Gateway Access Control Protocol (GACP)
194 Internet Relay Chat (IRC)

197 Directory Location Service (DLS)
389 Lightweight Directory Access Protocol (LDAP)
396 Novell Netware over IP
443 HTTPS

444 Simple Network Paging Protocol (SNPP)
445 Microsoft-DS
458 Apple QuickTime

546 DHCP Client

547 DHCP Server
563 SNEWS
569 MSN
1080 Socks