I don't know if anyone out there uses 37 signals products, but they are great! I use Backpack every day. Anyway, they just came out with a new one and it looks great. Highrise is kinda like an address book, but its also allows for collaboration, with shared to-do lists, emails, pictures, etc...

For me, working from home far away from my associates, this is going to be great for keeping in touch.

Anyway, here's the site: http://www.highrisehq.com/, free signup.