This is my first attempt. I did it all free-hand and I'm sure there is a better way.

Any actions or templates that you recommend for this sort of thing?

The one thing I see right off that I would fix on this one is that pics one & three need to match more closely in subject size.

Anything else?

Not bad for just eyeballing it... Although I used to be able to do cubed roots to some number of decimal places in my head, for some reason I always have trouble getting triptychs properly measured and aligned. I am sure there are some sort of actions, but I rarely do those,so I have not looked. :-)

As for the frame, I really like "Mikes Framer" for CS3/CS4. He charges something minimal like $6 but it does a lot. (A lot of really cheesy stuff too, but the good stuff actually looks good) You might want to check out his plugin.
http://homepage.ntlworld.com/pooternerds/Framer/index.html

Thanks, I'll check it out.

Jim, this is nice.

To my eye, the 'dark' shots should be on either side with the 'white' shot in the middle to create a bit more balance.

That's an interesting observation. It would also lead to a story line of the dog being tired after a day of modeling if I put the center shot on the right.