SOFTBEND Great because takes almost no CPU and highly customizable (I use to only show tempreature in a small text format on the bottom right of my screen). However, seems to not handle the new sensors of the latest PowerBook. Too bad. I had to switch to Temperature Monitor, which is not so convenient because unlike XRG, you cannot access prefs with a CTRL-click on the window (I usually disable the Dock icon for these kind of application, therefore it has no menu bar anymore).
(Version 1.1)