List of common ports

Here's a list of the most common ports that are in use. A more complete list can be found at :
http://www.iana.org/assignments/port-numbers

0 to 1023
1/tcp: TCP Multiplexor
7/tcp: ECHO protocol
7/udp: ECHO protocol
9/tcp: DISCARD protocol
9/udp: DISCARD protocol
13/tcp: DAYTIME protocol
17/tcp: QOTD (Quote of the Day) protocol
19/tcp: CHARGEN (Character Generator) protocol
19/udp: CHARGEN protocol
20/tcp: FTP (File Transfer Protocol) - data port
21/tcp: FTP - control (command) port
22/tcp: SSH (Secure Shell) - used for secure logins, file transfers (scp, sftp) and port forwarding
23/tcp: Telnet protocol - unencrypted text communications
25/tcp: SMTP (Simple Mail Transfer Protocol) - used for sending E-mails
53/tcp: DNS (Domain Name Server)
53/udp: DNS
67/udp: BOOTP (BootStrap Protocol) server; also used by DHCP (Dynamic Host Configuration Protocol)
68/udp: BOOTP client; also used by DHCP
69/udp: TFTP (Trivial File Transfer Protocol)
70/tcp: Gopher protocol
79/tcp: Finger protocol
80/tcp: HTTP (HyperText Transfer Protocol) - used for transferring web pages
88/tcp: Kerberos - authenticating agent
109/tcp: POP2 (Post Office Protocol version 2) - used for retrieving E-mails
110/tcp: POP3 (Post Office Protocol version 3) - used for retrieving E-mails
113/tcp: ident - old server identification system, still used by IRC servers to identify its users
119/tcp: NNTP (Network News Transfer Protocol) - used for retrieving newsgroups messages
123/udp: NTP (Network Time Protocol) - used for time synchronization
139/tcp: NetBIOS
143/tcp: IMAP4 (Internet Message Access Protocol 4) - used for retrieving E-mails
161/udp: SNMP (Simple Network Management Protocol)
179/tcp: BGP (Border Gateway Protocol)
389/tcp: LDAP (Lightweight Directory Access Protocol)
443/tcp: HTTPS - HTTP over SSL (encrypted transmission)
445/udp: Microsoft-DS SMB - used for file sharing
514/udp: syslog protocol - used for system logging
540/tcp: UUCP (Unix-to-Unix CoPy protocol)
636/tcp: LDAP over SSL (encrypted transmission)
666/tcp: id Software's DOOM multiplayer game played over TCP
993/tcp: IMAP4 over SSL (encrypted transmission)
995/tcp: POP3 over SSL (encrypted transmission)

1024 to 49151
1080/tcp: SOCKS proxy
1352/tcp: IBM Lotus Notes/Domino RCP
1433/tcp: Microsoft SQL database system
1434/tcp: Microsoft SQL Monitor
1434/udp: Microsoft SQL Monitor
1984/tcp: Big Brother - network monitoring tool
3128/tcp: HTTP used by web caches and the default port for the Squid cache
3306/tcp: MySQL database system
3389/tcp: Microsoft Terminal Server (RDP)
5190/tcp: AOL and AOL Instant Messenger
5222/tcp: XMPP/Jabber - client connection
5269/tcp: XMPP/Jabber - server connection
5432/tcp: PostgreSQL database system
6000/tcp: X11 - used for X-windows
6667/tcp: IRC (Internet Relay Chat)
8000/tcp: iRDMI - often mistakenly used instead of port 8080
8080/tcp: HTTP Alternate (http-alt) - used when running a second web server on the same machine (the other is in port 80), for web proxy and caching server, or for running a web server as a non-root user. Default port for Jakarta Tomcat.
8118/tcp: Privoxy web proxy - advertisements-filtering web proxy

49152 to 65535

Unregistered Ports
These are ports that may be in common use, but that are not formally registered with IANA. Where the use conflicts with a registered use, the notation CONFLICT is used.
1337/tcp: WASTE Encrypted File Sharing Program
1521/tcp: Oracle database default listener - CONFLICT with registered use: nCube License Manager
2082/tcp: CPanel's default port - CONFLICT with registered use: Infowave Mobility Server
2086/tcp: Web Host Manager's default port - CONFLICT with registered use: GNUnet
5000/tcp: Universal plug-and-play (UPnP) - Windows network device interoperability; CONFLICT with registered use: commplex-main
5223/tcp: XMPP/Jabber - default port for SSL Client Connection
5800/tcp: VNC remote desktop protocol - for use over HTTP
5900/tcp: VNC remote desktop protocol - regular port
6881/tcp: BitTorrent - port often used
6969/tcp: BitTorrent tracker port - CONFLICT with registered use: acmsoda
27960/udp: (through 27969) id Software's Quake 3 and Quake 3 derived games
31337/tcp: Back Orifice - remote administration tool (often Trojan horse) ("31337" is the "Leet speak" version of "Elite")