I usually use cuttingedgetesting.com (it's local to me).  A good source for finding a place near you is porn stars, they know places that are cheap, easy, efficient and they aren't at all surprised as to why you are there.

Lately I see 2-3 girls a month.  One very regular, one semi regular and the last is whatever whim strikes me.  I'm aware that the two I see most regularly also get tested (have seen results), otherwise I'd probably go monthly.

Any one has compared planned parenthood with other provider ?

std.about.com  Plug your zip code in and it will give you a list of available facilities.  Private pay, insurance or slide scale fee for service type.

Many cities big enough to have a Health Dept (e.g., New York, but many smaller cities, too), sometimes offer testing through their clinics.  In a big city, there are many small clinics so you can go out of your neighborhood.  Smaller cities, I don't know.  I guess it could be embarrassing to go to the clinic and see your neighbor at the receptionist's desk:  

"Hi, what are you doing here?"  
"Uh, ... wrong door ... I was aiming for the MiniMart next door to buy a magazine."
"How did you get up here to the third floor?"
"Uh, I thought, maybe, their high class magazines were on an upper level."

Of course, you might take a different approach:

"Hi, what are you doing here?"  
"I've been bangin' your daughter and I'm a little concerned about her rash so I'm here for a test.

Your GP/ob-gym should always have a reason to be compelled to perform full panel test. Yes, health care providers may judge for the truth behind this industry. He or she should know that non-monogamy is a main factor. If you want to deflect from yourself, you can say that your significant other is not monogamous with you.