Further to the discussion of free/vmstat and monitoring memory, I dug up some old articles that explain how to interpret the output of some tools.
Using top: http://ertw.com/~sean/news/Aug-23-2001.html Using free: http://ertw.com/~sean/news/Aug-30-2001.html Using vmstat: http://ertw.com/~sean/news/Mar-7-2002.html
Sean