One Shall Pass is a browser-side service for calculating strong, site-specific passwords. It is open source. In contrast to other password services, 1SP does not save your passwords or universal passphrase anywhere.
This page is self-contained, with only inline JS and CSS, and no images. So you can conveniently save it or use it offline. You can also watch your network monitor to witness it makes no remote calls beyond the initial page load.
There is one (optional) networked feature: if you're afraid you'll forget what you called a host (e.g., "gmail" or "google" or "gmail.google.com") or your features for a host (how long you want the password to be, etc.), you may login to oneshallpass.com. This will push and pull your encrypted hostnames and settings to and from oneshallpass.com. It will not sync your universal passphrase, so oneshallpass.com cannot access your passwords. Nor can oneshallpass.com read your settings or hostnames. So do not lose your passphrase, since it's not recoverable.