Ive got a similar problem. what kind of computer do you have?
Are your fans running properly? How about dust? it can get very dusty if the computer is over a year old. Clearing out the fans and heatsinks can drastically cool your system. Also have you added any new hardware recently like hard drives or a new gfix card? perhaps a new power source?
mine is a dell dimension 8400 and I am probably going to move the guts to a new case to improve airflow. My case now (the one it came with from dell) doesnt have a spot for a front fan and only has a 92mm rear fan. I am going to buy a new case that has a front 80mm and a rear 120mm so air can get in and out more efficiently and the heat will go with it. I'm not suggesting you do this, just saying this is what I plan on doing.
Here is a link to a program called "SpeedFan" it will tell you various temperatures like ambient/local/hd0/hd1 and depending on your motherboard may be able to set/change your fan speed
http://www.almico.com/speedfan.php