A few questions (these are closely related enough that they should be grouped):


1) How many online medical/testing companies test for STDs without a
doctor's visit?

2) How long does it take to get results from these online companies?

3) How much does it cost (to the company) to send out samples to a lab
and get results back? (not the price to the consumer, rather the
pricing before markup)

When you said getting test for STD without doctor's order, this is
call direct access testing.  Direct access testing (DAT), also known
as "direct-to-consumer" or "patient-authorized" testing, allow patient
to order, pay and received results for lab tests that they ordered. 
Tests that are offer are the same medically accepted lab tests ordered
by physicians.  Most laboratories that provide DAT accept orders
online, so customers can order and pay online, print out the request
and take it to a drawing station to have their blood drawn, some
laboratories will even send phlebotomist to customers? home or office
to perform phlebotomy.  As of March 2003, DAT is allowed in 34 states
and territories of the 34 states that allow DAT, 20 states have no
limits regarding DAT, while 14 states have limitation on what DAT can
provide.
The following sites offer DAT

http://www.healthcheckusa.com/
http://www.questdiagnostics.com/patient/index.html#questest

Hope this help.