I really like the 3 products from 37signals, Backpack, Basecamp, and Highrise. The latest updates to Basecamp are demonstrated below in this screencast and speak to the easy of use and elegant simplicity that are a hallmark of all 3 product offerings. I’ve blogged about previous updates here and here. Unlike other companies they don’t rush to overload the product with so many features that they loose the simplicity of it in the process.
I highly recommend trying out all 3 for personal or group / organizational use. They do have free offerings in each you can start there to get a feel for them and then you can upgrade as you need or wish. It is a great way to boost productivity among work or volunteer groups. If want to know more about how I have used them personally or for church use, just let me know and I’d be glad to chat with you about it.