App type: Browser add-in
Publisher:  LogMeIn
Price: Free, with premium version at $12 per year

Download XMarks (separate downloads for Firefox, IE, Chrome, and Safari)

By this point in time I'd imagine that virtually all power users, most readers of this site, and indeed most Windows users in general have two or more web browsers installed on their PCs. As important, we all use a divergent array of devices, with mixed Mac and PC households, Android phones and iPhones, and so on. With all this different, well, stuff, it's getting harder to maintain a consistent set of favorite online destinations across these different devices and browsers.

Not surprisingly, browser makers are themselves offering interesting capabilities around sync, usually for bookmarks but in some cases for other in-browser capabilities. For example, Chrome has an excellent facility for syncing web apps, autofill, bookmarks, extensions, passwords, preferences, and themes between browser installs. And Firefox offers a slightly more difficult-to-use sync capability for bookmarks, passwords, preferences, history, and (open) tabs, and it works somewhat with mobile versions of Firefox as well.

These capabilities are great, assuming you want to just use the same browser, and possibly move only between different PCs, or perhaps between a Mac and a PC. But for those of us who move between browsers, it's not enough. And that's where XMarks comes in.

XMarks is a browser add-in, or extension, for Chrome, Firefox, and Internet Explorer (and, on Mac OS X, Safari) that synchronizes data between browsers. It began life as Foxmarks and, as the name suggests, the original versions were for Firefox only.

So why use XMarks? For starters, it achieves the basic goal of syncing bookmarks between different browsers, and different browser versions, from different vendors, and running on different platforms (Mac, PC) if that's a need. So you can use Firefox on Windows, let's say, and Safari on Mac OS X, and your bookmarks will always be synced between the two. Or sync bookmarks between your work-issued PC running IE 7 and your home PC running IE 9. You can mix and match as needed.

But XMarks also offers some unique functionality that no individual browser offers. This includes backup and restore: Xmarks will store any changes you make to your bookmarks (additions, deletions, edits) for three months, so you can "go back in time" and restore your bookmarks to previous state. It provides online access to your bookmarks via my.xmarks.com so you can view, edit, add, and delete bookmarks, even if you're using someone else's PC.

There's also bookmark sharing, RSS viewing of your bookmarks, the syncing of open tabs (akin to the new Firefox 4 feature), and even profile syncing, which lets you create different sync profiles (work, home, or whatever) so you can keep your personal stuff personal. And on Firefox only, for now, you can also sync browsing history if you'd like.

Step up to the paid Premium version--at $12 per year--and you get access to an XMarks mobile app for iPhone and iPad, Android, and Blackberry with open tab sync, a more expansive backup and restore capability, and priority support. I haven't done this yet, as I use Windows Phone, but I could see this being a great capability for those who start reading a web article at work but then want to finish it on their phone during the commute on the way home (among other scenarios).

XMarks is a great cross-browser, cross-platform solution for this increasingly heterogeneous world. Highly recommended.