Gizmodo has a good list of sites that offer 2FA, It's Time to Enable Two-Step Authentication on Everything. Here’s How.. As I learned it's kind of important to do this because now if someone gets your password, the first they do is change it and enable 2FA so that it's more difficult for you to get your account back. I've done this for most of the sites listed here and it's simple enough to do and after you get all your devices enabled it's no extra work.
It is important to remember that when you get rid of a device you should disable its 2FA first. Also if the site gives you one-time use codes (aka backup codes), keep them in a safe place where you can find them if you need them!