Firefox: Mozilla's previously mentioned Weave project has been a great way to sync nearly everything about your Firefox setup between computers for awhile, despite its experimental label. The add-on has finally graduated from Mozilla Labs, though, renamed Firefox Sync and set to be packaged with future versions of Firefox.
You can still get it as an add-on now, under the new name and complete with a few new features such as availability in 15 languages, a simpler setup and one-click access to all your synced tabs. Plus, it's built to be the perfect companion to the upcoming, previously mentioned Firefox Home, so you can keep your data synced between all your devices.
Firefox Sync is a free download, works wherever Firefox does.