Well it depends on what kind of flash photo viewer you want, but if YOU want to crete one. You can easily make a simple viewer using basic Action Script 2.0 and use buttons o navigate your way along the timeline and have fifferent images on each of the frames.
There are plenty of tutorials out on the net. Try googling it
I did a bunch of searching, came up with lots of commercial "scripts for sale" stuff.
I ended up using spry tabs right in Dreamweaver. Not the best way to do it but it works.
You don't have to make the slideshow in flash.
Javascript is a great alternative and is compatible with every browser.
Slideshow 2 is a great slideshow.
It's easy to implement and it looks great.
You can find more information on this page: http://www.electricprism.com/aeron/slideshow/