For contacts (address book), the current plan is still to find people to port Sbook to Linux to do at least as much as it currently does on Mac OS X.
Thunderbird/Sunbird are the fallback of choice for calendar (i've already uninstalled Evolution, it's that bad), but i don't know how to sync them except by actually entering all data in Google Calendar which is an ugh (but what i currently do).
And trying out Getting Things Gnome