I've actually gotten quite a few of my laser diodes from "dead" dvd drives on ebay. They generally sell for less than $10 plus shipping... Now 100% of the drives I've purchased that were dead have been working red lasers in them. You may not expect to get as much power out of a dead drive as you do a brand new one but it's still a higher powered diode nontheless.
Closed cans are generally easier to work with, but open cans can handle much larger currents and are capable of putting out more power. However open cans are very fragile physically.