Program for finding duplicate files

Does anyone know of a program that will compare 2 folders for the same files (mostly pdfs that would have different file names in each folder). I guess something that would compare files based on their content (byte for byte ... maybe, I don't know) this should be simple once Tiger comes out with Spotlight I hope.

What would be ideal is a program that allows you to drop a folder onto it and it would scan through all the sub-folders then compare it to another folder and all its files within it.

What about something in the Terminal (any commands able to do this)?

Thanks

 

After trying some out, found zsDuplicateHunter to work great. Compared by size and checksum and found a wack of files.