Whereabouts is an app that allows you share your Address Book contacts over the Internet.

You can publish the contacts you want to share and choose to host them either in the Sites folder of a .Mac account or via FTP on your web server. You can also subscribe to the published cards of others.

The interface is simple and attractive and collapses to look like iSync:

When adding a contact to publish, you can choose which fields on the card to share, whether to pass-word encrypt the file and where to host it:

Whereabouts might suit a small business environment that is too mobile or dispersed to make use of address-o-sync, another utility that will share Address Books over a local network via Rendezvous.

UPDATE: Check out Brady’s review of how it works for his company in the comments to this entry.

Whereabouts is freeware and available from the developer’s (delightfully retro) web site.

Address-o-sync allows you to share and sync contacts from your Address Book with other users over a Rendezvous network.

Set-up is ?ɬºber-easy. If you are using Mac OS 10.3 or better, the Macs will simply find each other.

You can choose to share only certain groups, which means work-related contacts can be shared, but private contacts kept private. You can also password-protect the sharing, restricting who on the network can — and who can’t — get access.

Address-o-sync is donation-ware for individuals, but shareware for companies, and is available from the developer’s web site.