Okay, I'm thinking of a Looney Tunes short which features Bugs and Daffy and is set in 1492. It's about Columbus's voyages. What is it called, and is it on one of the currently available DVDs?

Is there a Looney Tunes reference website out there with this sort of information?

Perhaps you are thinking of Hare We Go?

There's no Daffy, but it's the only WB toon I know of with Columbus.

I can't recall one with Daffy either. The only one with Columbus I remember is the one listed above.

Here is an excellent site for WB cartoon references.
http://members.aol.com/EOCostello/

I think it is "Hare We Go". Is that one where Columbus goes around landing everywhere, posting a flag and saying "I claim this land in the naaaaaaame of Spain!"