Any of the htpc frontends can do it...Meedio, Xlobby, MediaPortal, GotAllMedia, maybe even MCE. They all have different ways of doing it and you'll have to rip the discs outside of the frontend, but sorting and playing them is a snap. Most will also let you either keep them in an ISO/dvd folder structure, or keep them as a library of xvid/mpg/avi/etc files. For the ripping process, have a look at doom9 for the various ways and means.