Thanks for all the advice. It turns out that a program I already had, SpeedFan, did pretty much what I wanted once I figured out how to use it. I can't say how accurate the temperatures are, because the number on the "Readings" tab was ten degrees Celsius higher than the graphed number. But the SpeedFan GPU graph matched RivaTuner's measurement.
The reason I started looking at temperatures is that I just now installed a new CPU cooler, a Zalman CNPS9700 LED. (I think I'm in love. The only way it could look any better would be to have Miranda Kerr near it. It looks like the main heat exchanger for the Infinite Improbability Drive.) According to SpeedFan, it dropped my idle temp from 26 to 18. I had been running the stock AMD cooler that came with the Phenom 9950BE. With the old cooler, CoreDamage drove the temp up to 57. The Zalman holds it at 38. Interestingly, the tested temps were all two degrees cooler with the side off the case.
The Zalman has a 3-pin fan plug, which means you get no mobo control (remind me to disable that in BIOS). It comes with its own little doodad with a knob on it and a long cable to adjust the fan manually. You can mount the little controller inside or out. I don't like that very much, because being who I am, I have to crank it to full and leave it there. The fan is pretty quiet, though.
There's the report I thought I owed y'all for your kindness. I paid about $2.50 per degree Celsius at max CPU usage. I think it was worth it.