Just so ya know, we (TechSoup) had an article penned by Chris Peters that was published earlier this month on this exact topic.

Extending the Life of Your Computer covers a variety of tips on how to get the most out of your hardware and even advice on converting it to other functions to keep it out of landfilles (or hopefully, recycling bins) even longer.

Check it out and feel free to add your thoughts and additions to the article in this thread.