There's a dev update for BottomFeeder posted with tabbed browsing in. I'm about to start a build, so that I can push up new builds that have the latest stuff, without the need to grab updates. There's a new tab item on the toolbar, as well as a menu pick. Each tab also has a small menu allowing you to tear a tab off or close a specific tab.

I would have had this done sooner, but it took me a bit to realize that menus for tab items were an extension added by TypeLess (the IRC plugin) - and I was missing a crucial (but not so obvious) bit of the API. I got that handled, and it's working nicely now.