I found this useful article link on Digg.com. The website is one I hadn't seen before, LowEndMac.com. If you own a Mac with OS X, it is a useful read. Some of it you may know, other information may be new to you.
"Every now and then, my Macs begin to feel a little sluggish. There are many potential reasons why: I tend to run 8-10 applications all the time - and sometimes push 15 or more. This alone will bog down any Mac. At other times, I realize that it's been weeks since I restarted the computer, and a simple restart will solve a lot of these woes. When those don't speed things up, I've found a number of things I can do to encourage my Macs back to their youthful snappiness. Here are a few tips I've found for restoring my Macs to full speed without spending a penny." Check Out the Article