My general recommendations:
1.) The certifying agency is mostly irrelevant.  Find a good instructor and
take whatever certification he offers.
2.) When you take your open water course, don't take any other courses.
Focus on the material presented and try to become the best OW diver you can.
Practice the skills for a while.  Learn bouyancy control!  Once you've got
bouyancy down and you're fairly well versed in the OW topics, then you can
expand your training into the different specialties.  Popeye may disagree
because his experience was somewhat different (IIRC), but IMO he's more the
exception than the rule.

There's not enough difference between them to argue about.

Select a good instructor and take the card he gives you.

esg

First of all, you are not legally required to be certified to dive...

http://grumman581.googlepages.com/scuba-certification

If you do choose to get certified for convenience or whatever, the
agency is less important than the instructor... We've discussed this
in the group many times... Check the Google Groups archives and you'll
find quite a few threads on this subject...

paul <moo@moo.iinet.net.au> pounded away at his keyboard resulting in:

My suggestion is to get good at diving before you start photography.

Dan Bracuk
Never use a big word when a diminutive one will do.

I"m pretty much in line with everyone else here.   I started with NAUI and
wound up with PADI because I liked the instructor better.  It was just a
better fit.  As others have said, your instructor makes a huge difference,
and after meeting him or her you should know if it's going to work within 5
or 10 minutes.  Once you complete the pool session you will have to complete
your certification in open water (OW).  You may decide to do this locally
with your instructor or another, or finish on vacation.  You must complete
your certification in OW to get your card.  IMHO PADI and NAUI are the two
that are best known, but the others will still get you a card.

I lucked out in that my final cert (OW) was in a class of one -- me.  The
one on one instruction was fantastic and I learned a lot as once again my
instructor was a good fit.

Any other certifications you get are up to you.

Thanks all!

Paul

The quality of teacher has been mentioned elsewhere. Another consideration is the
dive-shop associated with the course. This is because there will be pressure put on
you to buy your gear from the shop.

Adam

Talk to the instructor.  You won't have any idea about his scuba
skills, since you have nothing to judge them by.  But figure out his
personality.  Try to get an idea of his teaching skills.  Find out how
long he's been diving and teaching.  Ask him what his student to staff
ratio is.  And, if he's a she, ask what she looks like in a bikini and
if she wears a suit under her diveskin (used to have a DM that didn't.
She'd ask me to have all the students face me while I did some inane
lecture and she's strip down and suit up.  Very pleasant for me,
except the first couple of times.  Fortunately I don't wear skin tight
suits.)

Oh yeah.  You won't be able to do the UW photo course while you're
doing open water.  You need the OW to take the course.  And a good
instructor will tell you to dive some before you take the course.