[rhblake]

FastMail supports CalDAV. I use my FastMail calendar with Thunderbird (Lightning) and on my iPhone; works great. They also support CardDAV for contacts. /satisfied FM customer since ~2008 or so

[zamalek]

I had to purchase a CalDAV and CardDAV app (which were extremely cheap, mind) for Android, so it's not quite as plug'n'play there.

[smichel17]

Why is jjawssd's (sister) comment dead? Davdroid works great and is free (as in beer and speech), though I would encourage people to donate if it's useful to you.