You get vocal sample packages at primeloops.com and I think Mutekki also has some, as well as Zero-G.
Not a fan of such things, tbh. It all sounds really cheesy to me and often autotuned, propably they cannot stay in tune otherwiese, like many thin voiced singers in pop business nowadays
On the other hand, we have a good singer and I can sing a little myself as well, so it's easy to say I don't use these things.
P.S.: If you are looking for samples of movie dialogue, check loopmasters.com
You can also check at Find A Remix Contest - Remix Comps
regularly, sometimes good bands offer their stems, usually the contract doesn't allow posting the remixes anywhere, so it's not of much use if you don't win.