Any recommendations? Which one is easy to use?
Speedfan. That said, my advice is to only mess with the case fans. The CPU fan is probably nowhere near the noise source you think it is, and it's just too risky with respect to potentially running the CPU over safe operating temps. I've seen some weird stuff happen with CPUs that were only a few degrees overtemp, and still well within what the manufacturer reported as their operating range.
On a related note, run a Pentium III with a core temp of 53C and see what happens. 69C max, my ass.
Obligatory warnings out of the way, here you go: http://download.cnet.com/SpeedFan/3000-2094_4-10067444.html