If you're like most users, you've accumulated years' worth of bookmarks in your browser--a collection you definitely don't want to lose. Fortunately, it's a snap to back them up to the most logical place I can think of: the Web.
Firefox users should install the free Foxmarks plug-in, while Internet Explorer users can accomplish the same thing with BookmarkSync. These tools automatically copy your browser favorites to the Web, where you can access them from any PC (handy if you're working on someone else's system and need to recall a favorite) and restore them to your machine if the need ever arises.
Even better, both plug-ins can keep your bookmarks in sync across multiple PCs (home and work, for example), which is insanely handy. I've also used this feature to help with migration to a new machine, as it sure beats trying to manually dig up the browser's Favorites file, copy it over, import it, and so on. Foxmarks recently added the option to sync your passwords, another incredibly useful feature.
BookmarkSync and Foxmarks are freebies. I can't recommend them highly enough.