Having been in the autism world for over 6 years now, I'd have to say, hands down that other parents are your best resource for information about your child's autism.
Of course, still go through the Pediatrician but follow your gut if they say, 'wait' or 'give it time' or 'boys are slower to talk than girls'. Our pediatrician didn't catch it. We went through our county for an evaluation. One day, I received a message from my son's new teacher who told me he qualified for 4, 1/2 days of school....he was 3. Even then, the word 'autism' was never spoken. He was speech and developmentally delayed. He started school and I started parent support meetings. At the second meeting I questioned developmentally delayed and a mom turned around in her chair, looked at me square in the eye and said, "Your boy has autism. They can't tell you he does because they would be responsible for all expenses if you didn't have insurance. Get yourself a Developmental Pediatrician right away." I went home in tears. He had autism but no one used the word AUTISM and what was a Developmental Pediatrician???
I found our local Developmental Pediatrician and was put on an 18 month waiting list. Unbelievable to me. I couldn't apply for medical assistance without an official diagnosis so I was waiting. Talking with another mom she told me how to get around the 18 month waiting list. Ready? I'll share it with you. When you get the extensive questionnaire to complete for the Developmental Pediatrician, also send back a copy of any sort of evaluation you had ever gotten on your child. This way, you don't need a 'team meeting' with the Doctor, only a one on one. I copied the school's evaluation and when he was 2, he received speech through a speech therapist and guess what......we were seen by that same Developmental Pediatrician in UNDER 2 WEEKS. Got that? 18 month wait reduced to under 2 weeks.
I then began to search online and found myself on facebook...imagine that. Anyway, I found that many adults on the spectrum have their own pages. I now follow many of them and if I get stuck, I just ask them. They give me a different way to look at things..my son's way. I am very thankful for that.
In short, I can list a bunch of websites or Doctor's names but save yourself time and talk with other parents. Others that have been there...done that. Get involved in a support group through your child's school or local autism agency. They can direct you where to go and how to get their faster..my experience anyway.