Take a look at NextGenGallery it's pretty easy to set up. I can't say it's good for seo but it works well and it's free. It's not just a slide show plugin but you can use it for that.
nextgen is soooo bloated and personally has a bit of a learning curve.... a simple slideshow can be made with jquery cycle, much less code,=faster site
Bloated means nothing to people who don't write code. It makes little difference if you host is fast and you have a small amount of images. People sure do like to complain about free stuff that actually works. Simple doesn't mean better. Check them both and see for yourself. I'm pretty happy with NextGenGallery.