FavBackup is an easy-to-use portable tool which can quickly back up your Firefox, Chrome, IE, Opera, Safari or Flock settings and data.
The simplest way to make this happen is to run the program's Full Backup Wizard for your preferred browser: just choose where you'd like to save your backup and FavBackup will make it happen.
If you'd like to get more selective, though, opting for a regular backup will provide a lengthy list of the details you'd like to preserve. So for Firefox, say, you're able to save bookmarks, cookies, download history, extensions, history, MIME types, preferences, saved form data and passwords, site and user preferences, search engine, sessions, spelling dictionary, toolbar layout, themes and personas: just check a box next to the relevant item and it'll be included in the backup.
You can only make backups on demand, unfortunately - the program can't be scheduled to, say, automatically run a backup every day.
Still, backups are generally quick so this isn't a big deal, and if you're looking for a way to easily save and restore your browser configuration then FavBackup could be the ideal solution.