Coretemp is good for CPU core temperature, also I find the CPUID (or CPUZ) harware monitor is pretty good
alround for lots of temperature readings although it only gives definitions like MCP temp etc,
but it pays to know what they are anyway.

You can use the asus PC probe also that came with the board. I find it to read the same
as the other utilities.

The freeware version of everest displays most of the temps, at least all of the critical ones, the ones
it doesn't display you can get off CPUZ hardware monitor (which from memory is only the HDD temps)