If you are running out of room on your macbook than the video below will take you step by step on the process of upgrading your hard drive. In the video I use a 500GB hard drive for the upgrade. Below are also links where you can get this drive.
WHERE TO BUY: 2.5 SATA 500GB 7200RPM Drive
CompUSA.com $129.99: http://www.compusa.com/applications/SearchTools/item-details.asp?EdpNo=4434267&CatId=2682
Other World Computing $149.99: http://eshop.macsales.com/item/Seagate/ST9500420AS/
You didn’t address how to migrate the files/settings/etc. from the old drive to the new one. Any specific suggestions? (i.e. backup/restore program etc.?)