fruux takes care of your contacts, calendars and more so you don't have to.
fruux is a free service that takes care of your contacts, calendars and more so you don't have to. Never manually copy contacts and calenders between your devices again!
It also supports calendar sharing. That allows you to invite your family, friends or co-workers into an existing calendar and set individual permissions (read-only or read/write) for each person you are sharing a calendar with.
The new fruux is based on open standards and is no longer a Mac-only application. fruux from now-on also does a great job syncing contacts, calendars and tasks on iOS, Thunderbird, Evolution, Android (with a plugin) and other clients if they support the 'CalDAV' or 'CardDAV' standard.