Totally agree with all the previous recommendations and would add the following useful free utilities:
Onyx (
www.titanium.free.fr/pgs2/english/download.html) is a free tool for occasional maintenance and cleaning out of cache files.
Stuffit Expander (my.smithmicro.com/mac/stuffitexpander) is a free tool for expansion of various compressed file formats.
Useful websites for support help and news of the latest updates are:
www.macfixit.com
www.macintouch.com