I suffer of a psychological disorder. I have multiple personalities. Well, not in real life, but online I have various personas. Most notably I happen to use some of the same online tools both personally and for my everyday job. Of course the login info for each is different, something that can quickly turn into something painful.
Sxipper is an identity handling tool. It also provides OpenID (which I find myself using more intensively every day) as well as disposable email addresses for those sites where you feel reluctant to share a real email.
Although this two features would suffice to make it an interesting plugin, the real nice features in a time saving manner are the form autofill and persona-handling capabilities.
Auto fill works great because it is human trained. Each Sxipper user trains forms and makes that information available for everyone else. You can also re-train forms in case it is needed.
Using the auto fill in conjuction with personas is just perfect. I have two personas, personal and work. If I need to fill a form with my work contact information (email, address, phone, whatever) I choose that persona.
It is not a perfect tool, but it saves tons of time. Also it is in active development, and the guys at Sxip really listen to users, thus it just keeps getting better. If you feel reluctant to put all that information into a plugin of unknown origin, I might remind you that Sxip belongs to Dick Hardt,, that same guy who gave an awesome keynote on Identity 2.0 at OSCON.