In order to take advantage of extra keys in xfree w/fluxbox you can use xmodmap.
I have an Trackpoint USB Space Saver Keyboard, it has 87 keys and is lapsized. It includes a mouse, which is definately key for the lazy in me.
Using xev, I managed to find the keycodes for Web Page Forward and Web Page Backward. (233, and 234)
Then I wrote a text file for xmodmap:
! IBM Spacesaver Trackpoint USB Webpageforward and back keycode 233 = XF86AudioNext keycode 234 = XF86AudioPause
Then I included this in my .xsession file like so:
/usr/X11R6/bin/xmodmap /home/ashiant/.xmodmap
Finally I adjusted my fluxbox configuration to include the key bindings for these two keys. In the file ~/.fluxbox/keys I added:
None XF86AudioNext :execCommand xmms -f None XF86AudioPause :execCommand xmms -u
/usr/lib/X11/XKeysymDB for a list of symbols you can assign to the keycode that isn't doing anything.