Depends on the laptop. Some will be very very cool running and therefore wont come on very often. Others will be on all the time. Tell us what laptop you have and we should be able to tell you if it should be on all the time. My sister has a celeron M machine and it barely uses the fan. Also most Centrino laptops also tend to be rare users of fans.
Is the second part a separate question or do you mean you seek something like motherboard monitor? Google it its free.