With TPB it is possible to bind programs to the ThinkPad, Mail, Home and
Search buttons. TPB can also run a callback program on each state change with
the changed state and the new state as options. So it is possible to trigger
several actions on different events. 

TPB has an on-screen display (OSD) to show volume, mute, brightness and some
other information. Furthermore TPB supports a software mixer, as the R series
ThinkPads have no hardware mixer to change the volume.

WWW: http://www.nongnu.org/tpb/