With many college networks, you have to register your MAC address, as well as log on to the network. Both techniques are used to filter/restrict connections, however, in many cases the 2 are completely separate. For example, any registered MAC can be used with any logon, this allows students to share computers without compromising the administrators' ability to monitor individual activity, or individual network access in the case of shared drives and email for students.

It is a simple matter to spoof your MAC address and use a captured logon.

As for the port blocking, it is usually done at the firewall/gateway, but as fork mentioned, there are other methods.

Getting around these restrictions is usually just a simple matter of port redirection, although I would suggest using encryption for anything you do, mainly because of the distinct possiblity of your connection being sniffed.

EDIT: Yes, I know. I once again posted information on how to bypass restrictions on someone else's network. Screw the ethics, have fun. Don't call me for bail.