I know there is one out there, How do I read sheet music that someone posts a file link thing to? Where do I go to download a program that will allow it?

Try MidiNotate, that should read .not and .mid files.

Depends on which format they post the sheet music in.

.MUS = Finale
.SIB = Sibelius
.NWC = Noteworthy
.PDF = Acrobat Reader

You can also download 'viewing' versions of some programs, such as Scorch for Sibelius and I remember it's called Noteworthy Reader or something for Noteworthy.