Since you revived a dead thread, you can also get one just by going to the Apple store. Depending on the Genius, they might just give you one free.Calling general support is the answer: 1-800-275-2273. Very easy to order a new install disc for my macbook. Cost was around $17.60 with tax.
That applies for Tiger and Snow. Leopard was universal. I cloned a Leopard install from My MacBook grey disk onto an installed using my grey disk on to an AFP partition and dropped it into my old G4 Quicksilver as my DVD drive had broken so couldn't use my retail copy of Leopard at that time (I had no FireWire lead) It worked perfectly.No, the OSX version for intel macs is not universal, while some of the apps may be, the OS as a whole is not.