Hi,

the following kind of works for me now:

;; define function to add recent files button
(defun tool-bar-add-recent-files ()
  "Add toolbar button for Recent Files."
  (interactive)
  (tool-bar-add-item "~/.icons/emacs/clock" (lambda ()
                            (interactive)
                            (popup-menu (easy-menu-filter-return
                                         (recentf-make-menu-items)
                                         "Open Recent")))
                   'recent-files
                   :visible '(and (boundp 'recentf-mode) recentf-mode)
		   :help "Pop up the Recent Files menu")
)

;; write tool-bar-add-recent-files into all hooks
(add-hook 'text-mode-hook 'tool-bar-add-recent-files)
(add-hook 'LaTeX-mode-hook 'tool-bar-local-recent-files)
;(add-hook 'info-mode-hook 'tool-bar-add-recent-files)
(add-hook 'emacs-startup-hook 'tool-bar-add-recent-files)

There are still some problems with the info mode that completely
overwrites all tool-bar-map settings, don't know.

Is there any political will to add this to recentf.el? Many other
editors have this feature, so it would bring emacs up to standard
regarding toolbar features. David said that Aquamacs has it. As icon I
would suggest the attached clock.xpm, which is GLPL and it's a clock
like in Aquamacs.

Best,
Bernhard