I use password hasher / generation extension for browser, which makes sort of HMAC of password with domain. Then I use few master passwords depending on sensitivity of a site. But at the end - each site has its unique very strong password.

Firefox: https://addons.mozilla.org/pl/firefox/addon/password-hasher/...

Chrome (same algorithm): https://chrome.google.com/webstore/detail/pawhash/adgekjfphh...)