[ UPDATE ] LastPass has since released a Google Chrome extension, an iPhone App, Windows Mobile, Blackberry Android, and Symbian mobile apps which you may want to look into instead or in addition to the bookmarklets.
LastPass has just released 3 bookmarklets to extend the LastPass experience to all the other browsers and mobile devices in your life.
We're very proud of implementing our complete Form Filling solution in a bookmarklet too -- Now if you want to buy something on your iPhone at an online store with your credit card you can do it in 10 seconds rather than 15 minutes (or not at all), it's amazing.
If you're already an IE/Firefox LastPass user the experience is a little different -- you have to do some setup, and you have to activate the LastPass feature on each page -- but if you are on the road and can't install software, have a mobile browser, or like to use Opera, Google Chrome or Safari, this solution works quite well.
We've prepared a quick video covering setup and an example of the feature in Google Chrome:
To get started you'll want to go to https://LastPass.com/ and sign in then hit Bookmarklets. If you're a new user -- go through the installer, then use your LastPass plugin to get all your passwords working before setting up the bookmarklet.
We've also improved m.LastPass.com as part of this process to have a login simply activate your session, and your bookmarklets, rather than try to immediately download and decrypt all your data -- this is far more workable if you have hundreds of accounts, like many of you LastPassers do.
A number of people have asked how to setup iPhone here how it's done: