In PS 7 there is a reference to 'nearly 20 ghosts' streaming thru the back wall of the Great Hall. The only ones named (that I can find) are: Nearly Headless Nick, The Bloody Baron, The Grey Lady, The Fat Friar, Moaning Myrtle, Professor Binns, and Sir Patrick Delaney. Sir Patrick isn't a Hogwart's ghost - he's the head of the Headless Hunt. There are references to various other ghosts during Nearly Headless Nick's 500th Death party. And the Hogwarts ghosts say that they don't go to the Shrieking Shack because of the 'rough crowd' that hangs out there. Peeves is not actually a ghost, but rather a poltergeist. Not quite the same thing.
Lady Felula, Gryffindor House