I will probably build a whole section out of this page later this month. For now here is a list of all the "Well Known Port Numbers" based upon RFC1700 and http://www.iana.org/assignments/port-numbers
Do you want to perform searches for ports that are used by Trojans and Viruses? Try the Trojan port search engine found on my Other Search Tools page.
You should also read the following pages:
Your browser does not support inline frames or is currently configured not to display inline frames.