The best. Period. Rated 5 out of 5 stars
Used Roboform for years, with four licenses (two PCs, Palm app, and Roboform2go for my thumbdrive.) Lastpass, though young, kicks some serious Roboform ass. The seamless syncing is a dream... I can now access my passwords and logins from ANY internet connected computer without having to buy additional licenses like I would with Roboform. Bookmarklets that let you use LP in *any* browser (Opera, Safari, you name it.) The developers are very responsive, responding to users on their forums and regularly adding requested features.
And the security is top-notch. Everything is encrypted LOCALLY, on your PC--Lastpass's servers never see your actual data.
Try it. You'll wonder how you ever existed on the web without it.