shareable contact management solution?

The largest (afaik) open source project in this arena is http://www.sugarcrm.com/crm/, which has positioned itself as a clone of Salesforce. Most people's experience of Sugar, however, is that it is VERY overwhelming straight out-of-the-box. It may be overkill for what you need to do, and it's geared towards Customer *Relationship* management, which means it's got feautres more oriented to sales people than you'd find in a simple contact manager. Still, you might play around with a demo to see if it'll suit you. I doubt you're going to find anything as user-friendly and pretty as highrise -- 37signals has a 'let's strip everything down to the basics and make it beautiful' philosophy* that can be rare among programmers, most of who are racing to implement as many features as possible. * Unfortunately this philosophy means that a lot of their software is unusable for 'serious' projects without organizational 'hacks' implemented by the user. I'd love to use basecamp for project management, but it's missing a couple key features we need (or possibly that we just think we need).

You could do this with Filemaker. I'm pretty much trying to do the same thing right now for my own personal freelancing business, and FM is amazingly powerful. The downside is that you'd probably have to hire someone to set it up (it's pretty daunting to get it going if you haven't spent some quality time with a manual or two), the upside is that you can build your dream solution and the sky's the limit with what information you can track and how you can tie it all together. It has a web interface, server-client software, and runs on Mac/Windows. I've pretty much given up on trying to find a solution that has all the features I want which is why I'm going the roll-your-own route, everything I've looked at either doesn't run on Macs or needs some kind of 'hack' to get it to do the things I need it to like fishfucker said.