A Couple of More Websites...

I've ran across a parenting site giving the timetable the warning signs you should start looking for if you believe your child is having speech delays. I myself still have yet to be fully understandable at 4 years, which bought about me seeing a speech therapist at the beginning of my school age.

http://www.babycenter.com/0_warning-signs-of-a-toddlers-language-delay_12293.bc

The other was an interesting piece on figuring out the difference between a child that is having speech delays or a child that is just a late bloomer. There's not much in concrete symptoms separating the two, but it says that child that is more likely to be a late bloomer would use more gesters, understand speech at a pretty normal rate, and should have continuous, if a bit delayed, progress in language.

http://www.asha.org/public/speech/disorders/LateBlooming.htm

Fragile X Foundation Website

I found a website that discusses late speaking in boys due to fragile x syndrome. Fragile X syndrome is the most common cause of autism in children. It affects about 1 in 3600 males and 1 in 5-6000 females, with males typically showing the more severe symptoms in cognitive, physical, and mental development.

Males that have Fragile X will typically have some kind of speech development delay, and is usually one of the first signs that a child may have Fragile X. The amount of speech delay and language complications vary from child to child. Female children tend to not be affected in acquiring language, but may have a problem with conversational skills or pragmatics.

http://www.nfxf.org/html/late-speaking.htm