If you're into web technologies, one of the words being whispered for a good while now has been Microformats - a fantastic way to place human and machine-readable contact, calendar and other information in webpages.
Of course, in order to take advantage of Microformats and perhaps bring the information they offer onto your system, you need a browser that will read them - there's Firefox plugins, and NetNewsWire 3.0's built-in browser reads them. But what about Safari? Thanks to SIMBL, there's a small array of Safari plugins available and from the maker of Safari Tidy comes Safari Microformats. Whenever visiting a site with Microformats, an icon appears in the right of the address bar (not unlike the RSS icon). Clicking it brings up a menu of available hCards and hCalendars you can add to Address Book and iCal.
The Microformats plugin is a free download (with donations) and requires OS X 10.5 Leopard. I had problems installing the plugin due to issues with folder permission. If, like me, you can't get it to show up on sites that do have Microformats within the code, the following terminal command (via the SafariStand website) fixed it:
sudo chown -R root:admin /Library/InputManagers