There are dozens of choices and its mostly personal opinion what is best. I do my own organization of photo files into folders (directories) by year and occasion and then simply burn whatever set of folders I want to a CD or DVD using either Nero Burning or the Windows burning tool if all I want to a portable set of photo files to show. For more sophisticated slideshows, e.g. with music backgrounds and special effects, I've used Cyberlink MediaShow and Arcsoft's DVD Slideshow with good results and some others I don't recall.
And as Ned say, Movie Maker is free with Windows and works well enough.