Alternative to Shutterfly for slideshow

My friends and I are trying to accumulate photos to make a slideshow.  I figured a share site on shutterfly would be the easiest, but I am having trouble with the new format - I want the photos in a specific order and changed the file names so I could sort by file name, but many of the file names were changed (to things like 0007296610035726974.jpg), and the ones that retained file names aren't sorting correctly anyway.  And, I can't figure out how to sort manually, although we have so many photos that I don't know that I'd want to do that.

Anyway, I don't want to spend a ton of time on this so I'm hoping there is another site that I could try where we could just upload photos, sort by file name and be done.  Any suggestions?

Thanks