Ports used for Microsoft products
http://www.microsoft.com/canada/smallbiz/sgc/articles/ref_net_ports_ms_prod.mspx?pf=true
Firewalling?
http://www.microsoft.com/technet/prodtechnol/windowsserver2003/library/ServerHelp/428c1bbf-2ceb-4f76-a1ef-0219982eca10.mspx

To find out common port mappings, take a look at "/etc/services"

To find an extensive list, reference http://www.iana.org/assignments/port-numbers