Calibre is an interesting choice as it will let you put most any kind of file there (not just books). It doesn't DO much with anything but books, but you can edit, search change metadata, etc. It tends to work nicely for anything with titles, authors, etc. I use it for scanned-in sheet music, also keeping midi files along with the pdf's when I have them.
I've used JRiver Media Centre cataloguing and playback for a number of years and have always been happy - it can play just about any audio or video file and has very powerful tagging and editing features.