Here's a list of common TCP ports. You can find a more complete list here:
http://www.gasmi.net/docs/tcp.html.

Port Number	Service	Description
21	FTP	File Transfer Protocol
22	SSH	Secure Shell
23	Telnet	Telnet remote login
25	SMTP	Simple Mail Transfer Protocol
70	gopher	Gopher
79	finger	Finger
80	HTTP	Hyper Text Transfer Protocol (WWW)
88	Kerberos	Kerberos authentication
94	tivoli	Tivoli Object Dispatcher
110	pop3	Post Office Protocol Version 3
123	ntp	Network Time Protocol
137	netbios	NetBIOS Name Service
138	netbios	NetBIOS Datagram
139	netbios	NetBIOS Session
143	imap	Internet Message Access Protocol
161	snmp	Simple Network Management Protocol
162	snmptrap	SNMP trap
194	irc	Internet Relay Chat Protocol
389	ldap	Lightweight Directory Access Protocol
443	https	Secure HTTP
445	SMB	MS Server Message Block Protocol (file sharing)
500	L2TP over IPSec	Internet Key Exchange (IKE) (UDP)
563	nntps	Network News Transfer Protocol (nntp) protocol over TLS SSL
1433	sql server	MS SQL Server
1521	oracle	Oracle DB
1701	L2TP over IPSec	L2TP traffic (UDP)
1723	PPTP	Microsoft VPN (PPTP)
2401	cvs	CVS pserver
3306	mysql	MySQL DB
4500	L2TP over IPSec	IPSec Network Address Translation (NAT-T) (UDP)
5432	postgres	Postgres DB