Nice: I've been trying to settle on a project management solution that's more feature-rich than a simple ToDo list. A lot of folks I work with are smitten with (and use) Basecamp. It's a little overkill, perhaps, but sometimes you need to get the whole enchilada just so you can eat the guacamole. ..Or something.
Anyway, TrailGuide is a mobile client for Basecamp that will give you access to most of the key features you'll need to track and collaborate on your projects with Basecamp. It's a perfect example of why I generally prefer local software over interacting with my data over the web. There's a 30 day free trial, after which you're paying a per-month fee.
If you rely on Basecamp for project management and customer communication, start increasing your productivity by carrying your projects with you at all times - right on your smartphone - using TrailGuide from Carry The Day.