I went through all of this when I got my MacBook Pro. Forgive the pun, but around that temperature range you're cool
When researching this a while ago, I dug up a white paper at Intel's site about the Core Duo. It can run past 100 degrees C and still be within spec. When the CPU temperature hits 125C it performs an automatic shutdown to prevent physical damage.
My system averages around 70C under use with several apps running.
This website is a database of user-submitted MacBook and Pro temperatures. The link belwo sorts the results by temperature under load:
Intel Mac Temperature Database
A handy Dashbopard widget to have is iStat
. You can track many system resrouces with it at a glance. I have attached a shot of mine at this point in time.