Embeddable slideshow?

Are there any good slide-show creators that can be easily embedded into an existing site? Essentially I'm trying to avoid having to invent yet another slide-show implementation. So I'm looking for:

* Must have: Ability to embed resulting slideshow on my pages.

* Ideally: Allows me to embed the creator directly into an existing page. So some sort of widget or iframe implementation. Our users could upload directly and create the slide-show itself.

* Add captions to slides

For-pay is fine by me. What are your experiences? There HAS to be something out there to help me out.

Thanks HN!