Easy - use Apache with webdav to share a folder of calendar files. (This usually just means adding "DAV on" to the httpd.conf directory configuration, and setting permissions appropriately). Sunbird/Mozilla Calendar can access, publish, and refresh these remotely-stored calendar files.
Any documentation available on how to set this sort of thing up? Happen to know if it would work in Evolution? :-)
WebDAV tutorial: http://www.serverwatch.com/tutorials/article.php/10825_2176771_1
Calendar FAQ: http://www.mozilla.org/projects/calendar/faq.html
But really, it isn't that hard to implement (unless you get fancy with permissions). Just mess around with it a bit... I haven't used Evolution, so I can't say how it's calendaring works.
- Mike
