Since my journey into Google Apps use I've begun using it in my daily life. In the summer I ramp up the exercise from what I'm able to do--a combination of being a teacher and living in cold-wintered Minnesota I suppose.
I've created a Google Form template that I can enter in workout information to track my progress and total miles, pace and running excuses. There are other templates already out there you can also search in the Template Gallery.
With my template, I like to switch between biking and running and wanted the results to be separated out by exercise type. I also gave myself a place for an excuse each day and have those phrases placed into a word cloud in the "widgets" tab just for fun. For example, on the day of my 8 mile run I had a burger and root beer an hour before and noted that in the form.
I plan to bookmark the form as a web app on my iPod and just enter the data that way. I won't have to go into the actual spreadsheet unless I want to track my progress. Data is sorted into a totals table, a pace chart, which is based on the total pace and how it is hopefully improving... If you are only tracking one mode of exercise the pacing chart will probably make more sense.
I've shared it in the template gallery if you are interested in trying it out. (Click here)