If your in the habit of using Thunderbird at home and a web browser in College to access your Gmail account, then keeping your Address books synchronized can be automated using this Thunderbird add-on.
Google Contacts add-on adds bi-directional syncing for your Thunderbird and Gmail Address Books. Any change you make to your Thunderbird Address book will reflect accordingly in the contact list in Gmail and vice versa.
It creates a new Address Book for each Gmail account and synchronization takes place between that Thunderbird address book and the corresponding Contacts list in Gmail only, leaving the other Address books unaffected.
Google Contacts also works with Google Apps email account.
Godspeed
http://www.shubhspace.com/2009/01/synchronize-your-thunderbird-and-gmail.html#links