FogBugz On Demand now natively includes some authentication methods other than the standard username/password authentication.
Setting up authentication with Google's OAuth is quite simple for companies using Google Apps for work email. Once an administrator enables OAuth following the instructions in this article on Fog Creek Software's help site, logging in is as simple as clicking the OAuth button on the login page. All of the users' settings are retained.
If you’re already managing the rest of your authentication through a SAML 2.0 provider, you can also use your identity provider for FogBugz login. Steps for configuring SSO can be found in this article. This requires a bit more configuration than OAuth, but will work for companies that don't use Google Apps for email.
Of course, if you have any questions about configuring SSO in FogBugz, you can always contact customer support at http://www.fogcreek.com/contact/.