You guys... wow. That's nothing. My C2D will range from 35C-80C (95F-176F) on any given day depending upon the workload I'm giving it. Flash video (hulu, adverts) will increase the temperature of your chip. The core 2 duo runs a little hot. It's nothing dangerous for the chip or the other components in your laptop, however. It's rated as a max operating temperature of 100C (212F) in a mobile chip, I believe.
Also you have to compare similar units - a Core Duo will run hotter than a Core 2 Duo for the same processor intensive operation. Ambient temp will make a difference, as does the surface that the MacBook is placed on, viz fluffy table cloth as opposed to hard desk. My MBP was on stick on furniture protectors which actually lifted it another couple of mils, allowing a bit more airflow underneath.
My MacBook has been running for about 6 hours doing light-duty stuff, and the CPU temp is currently 61C (142F), perfectly normal for this machine. Fans are not running that I can hear, but I'm not going to lean over and check.