I blogged a few weeks ago that while AJAX applications are cool to look at, they really didn't provide much value to the end consumer or investors.
Today, I stand corrected, as I've begun using 37Signals online webware. They provide a service to help manager your life, as well as project management that makes MS Project look like a headache. It's all very nice looking AJAX, and it's a great service. Best of all it's free for limited personal usage and very cheap for commercial usage.
The features are too numerous to list here. I suggest you check it out if you're interested in the next generation of applications. It's definitely a valiant effort.