I brought my old Gimp Toolbar Patch up to date, it should work with Gimp-2.6 or the newest Gimp-SVN. In addition to the earlier patch it now supports two toolbars. You can customize them by copying image-toolbar.xml or image-secondary-toolbar.xml to ~/.gimp-2.6/menus/ and editing them as you like. The toolbar are hideable and showable just like the other UI elements. As you can see in the screenshot, not all actions have icons so they will show up by name. The patch is available at:
Prebuild Ubuntu packages are available from:
deb http://ppa.launchpad.net/grumbel/gimp/ubuntu lucid main
deb-src http://ppa.launchpad.net/grumbel/gimp/ubuntu lucid main
GPG key is F5E8C9BB, use "sudo apt-key add FILE" to add the key.
Or you can directly use:
sudo add-apt-repository ppa:grumbel/gimp
More information is available on the Launchpad PPA page.
Edit: The location of the packages has changed.