Has it lost some of the zing it used to have? Are you getting unexpected crashes and error messages? Is your Macbook getting hot and the fan running constantly?
If so, you need to download iBoostUp. The #1 free utility* on the Mac App Store(sm) (*as of Jan 19, 2012)
iBoostUp tunes up and optimizes your Mac by purging unneeded files, fixing your hard disk, giving you performance recommendations, protecting your privacy by removing cookies, displaying system information and much more!