Free and very popular. Download the program and also download the plugins. Don't install the google tool bar if the installation presents you with that (though it's not "evil" and can be removed if you install it by mistake). Decide if you want IrfanView to be associated with all the types of images it can display (Can be changed later if you set it to none. It's not needed to make a slideshow).
After installing, start it up and click on "File" and then "Slideshow" from the drop down menu. You can load your audio "MP3/M3U - MPEG Audio Files" (where it says "Files of type" in the top part of the right hand pane. By default it is set to Common Graphic Files so you need to click the arrow button next to that to change it.) and then switch to "Common Graphic Files" to add your pictures. Load the audio first if you want it to play at the beginning, otherwise it will start in order after the images listed ahead of it.
"Q: How can I add background sound for automatic slideshow or EXE/SCR?
A: In the slideshow dialog put/add MP3 files into the slideshow file list, usually at the begin or before an image. The MP3 file is played until it ends or until next MP3 is loaded from the file list. IrfanView PlugIns should be also installed, at least the MP3 PlugIn."
Lots of advanced options like building a slideshow CD that can autoplay.
"Q: I will create a CD-ROM with images and I will put IrfanView on the CD. How can I start IrfanView's Slideshow when I insert the CD in the drive?
A: You can create either a self running EXE slideshow file (in the slideshow dialog) or you can copy the original files to the CD and use a TXT file. Read the help file page "How to start IrfanView slideshow from a CD?" for examples."
http://www.irfanview.net/http://www.irfanview.net/faq.htmhttp://www.zisman.ca/Irfanview/Or .....
You can go an easier route for a hosted slideshow by way of Image Shack.
http://imageshack.us/http://imageshack.us/slideshow/http://news.imageshack.us/blog/?p=59Bottom link shows the add audio option.