is there a way to make a picture look like it is talking?

I have iStopMotion 2 for Mac: http://www.boinx.com/istopmotion/overview/

You can animate with it. But no, you can't animate with your existing software. Sorry. 🙂

I have the 99$ version of it, which has a feature called "rotoscoping" that lets you put audio in sync to a animation. I would highly recommend iStopMotion, as there are three programs for Mac in the animation category and iStopMotion is the best one, in my opinion.
As for your other question, I am using it on Snow Leopard and, aside from a couple small glitches, it works beautifully. The interface doesn't look like it came from Tiger-- it looks like it came from ten years into the future!
With iStopMotion, you can export your projects into Quicktime movies for later importing into iMovie, Final Cut Express, or Final Cut Pro. So you could make an animation with rotoscoping and then put it into iMovie to add titles or live action.
NOTE: Rotoscoping is only included with the 99$ version, but it's really worth it to make the upgrade.

Good luck in making your movie!

Oh, and by the way, thank you for giving me the "helpful" star in my first post! 🙂

Don't know for sure if this would work, depends on if the person talking is facing the cam or if it's a profile view. If it's a front on shot then make a still of the person, export to Photoshop, with a soft edge eraser erase the mouth area. Export back to iMovie as a transparent .png. Shoot someone speaking, as near the same size, lighting, color & location on the screen as the person in the still. Back in iMovie put the speaking layer under the still layer, align the mouth under the transparent area in the still & maybe you'll get what you want. There's many past postings here about how to make a transparent .png layer. Since you have Photoshop Elements, that's where I advise you to make the still, transparent and a .png.
Good luck & let us know if you can solve the problem, probably more than a few people wanting to solve the same thing.