I have always logged my workouts from the first time I went out for a short run. It's always cool to see that I can go faster or longer (or both), and without logging, that's impossible. I started out with a package that ran on my PC for logging my workouts, but it eventually suffered from data corruption issues and since it is so old it was not worth trying to fix. When I started riding, I found a web-based tool to track my rides which I really loved. Unfortunately, I took an 8 month break from riding a few years back, and when I started riding again I'd forgotten the URL for the site! To this day I cannot remember what site has a record of every ride I made for the first 3 years that I was riding. :-(
Recently, I've been using Map My Ride (www.mapmyride.com) to track my workouts. It is really great in a few aspects, most importantly in that I can track my run/ride on my iPhone and import it automatically into the tool. On the other hand, this application lacks in a number of very important aspects, most importantly in that it doesn't have any real graphing capabilities and I can't export to Excel or some other software package to do analysis.
I'm looking for a better system, but until then I will continue with Map My Ride. If you have any suggestions for a logging system (preferably one that won't go away and is easy to remember), I'd love to hear about it. Please leave any suggestions in the comments.