Pressing Ctrl+B in Chrome opens and closes the Bookmarks Toolbar. By default, Firefox Ctrl+B toggles the Bookmarks Sidebar. Here is how to apply the same shortcut key to Firefox as in Chrome. The Bookmarks Sidebar will still be accessible with Ctrl+I.
1. Tools > Keyconfig (Ctrl+Shift+F12)
2. Click once to highlight Boomarks Ctrl+B
3. hit Disable
4. Click Add a new key button or double click on Bookmarks
5. Change the Name to Bookmarks Toolbar and paste this code:
6. With Bookmarks Toolbar highlighted click in the box next to Apply and then press Ctrl+B. Hit Apply. Then Close. Restart Firefox
Make sure that the Bookmarks Toolbar is checked on in View > Toolbars in the Firefox menu. Hitting Ctrl+B should now toggle the Bookmarks Toolbar instead of the sidebar. The Bookmarks Sidebar can still be toggled with Ctrl+I.
Source: Firefox Support Forums
Another code is also posted in 2010 in the Firefox Support Forums. But the short form above does work in Firefox 3.6.x