If I scan a print for the purposes of showing it on the web I scan at 72 dpi, save as a small J peg (File size) and upload that when I need to.

Scanning negs and transparencies, I scan at 72 dpi, but size the output image to at least 8x12, Save as a smal J Peg as before and upload that as and when required.

I have photoshop but tend not to do anything to the images before uploading, just resetting the size if need be.