There are numerous programs that will display temperatures of all sorts of devices, although I don't know how accurant they all are.
I personally use motherboard monitor and it seems to work just fine.
Basically, any temperature above 60 degrees is a bit iffy, if you are in the 40s or lower you have absolutely nothing to worry about though.
Intel C2D E6320 / AMD Athlon X2 3800+
Gigabyte 965P DS3 / DFI nF4 Ultra-D
2GB OCZ Gold PC2-6400 / 2GB OCZ Gold PC4000
eVGA 8800GTS 320MB / eVGA 6800GS 256MB
150GB Raptor / 74GB Raptor
2x500GB / 320GB
OCZ GameXStreme 850w / OCZ StealthXStream 600w