Good college probability reference?

In my lecture tomorrow morning I want to compare and contrast discrete and continuous probability distribution functions. For example, in the discrete case the sum must equal 1. In the continuous case the integral must equal 1.

My text doesn't have this because it's afraid of the word "integral". Can anyone point me to a good reference for this, preferably online? (I came here after reading some of the worst Wikipedia articles I've ever seen.)

Of course I'll write it all on the board tomorrow morning but that doesn't help students who miss class. If you can find me a good reference fast you'll save me the trouble of installing LaTeX on this computer to make handouts!