My colleague recently showed me http://www.fitsw.com to help me manage my training business. I like it because it’s FREE and has a lot of features to help with managing client progress (cool graphs!), and a lot of features to manage workouts, diet etc. I can even integrate workout demo’s into the workouts for my clients. I’d give you more description of other cool features I use but I need to head over to the grocery store.
The one thing they could work on is the look (not a fan of their colors) but I’m able to get past it with all the features and its ability to increase my efficiency and allow me to manage more clients easily.