Is there any way to allow someone to download the whole shared Photos folder on Dropbox and not only individual files? Preferable a solution that doesn't require the receiver to register on Dropbox?
You could try this method posted on Mac OS X Hints:
Just stick the folder of files into your public folder, and head to the Dropbox webapp. Click on the folder you want to share, then click the “Get Link” button at the top of the page. Add ?dl=1 to the end of it, and send that link to your friends. It’ll zip the file up for them and download it to their computer. (Lifehacker synopsis)