One of my blessed finds is Sittercity.com. You have to pay a fee to have access to 1,000 of girls, but once on you can read reviews on each sitter/nanny left by other moms, pay $10 for a background check; you can see their education, religious beliefs, whether they're a smoker, how far they live from you, their picture (if posted), and more. While the title indicates "sitters", many nannies are wired to the site and you can gain access to them.
You can also advertise for a job and the girls come to you. You can weed through them w/o ever talking w/ them b/c you'll have their resume in front of you if they responded to your ad. I can usually tell in their cover letter whether I'd interview them (Christian, educated, sound fun, friendly, experience, etc. are a few attributes I look for).
There are other nanny sites, but I've been going through Sittercity for 2 years now and we have a list of sitters we can call at any give moment & have become part of our family.
Let me know if you have any questions. I'd love to help!
Blessings,
A.