Our son has developmental speech delay for an unidentified reason. At 3, when he was first diagnosed, it was for autistic-like symptoms, but as he grew it was agreed that it wasn't autism. We showed him the Brainy Baby series when he was young, and while it didn't seem to help him talk, once he did start talking we found out that academically he was way ahead. We also read to him every night since he was 1, and I think this helps too.
As for videos, I agree with the post about teaching your son sign language. If the speech issues are due to auditory processing disorder or expressive language disorder, your son may just be challenged to generate speech, not communicate. In this case sign language would be very helpful. Our son picked up on sign language very quickly, which told us he did not have a communication issue but rather a speech issue.
"Signing Time" are excellent videos to teach your son sign language. You might be able to find them at your local library to try them before investing in them. The woman who created them has a daughter who is deaf and her second daughter is disabled (I think cerebral palsy but not sure). The videos are interactive and fun. They use children to teach the signs in the video and they choose themes that help the children learn what is needed to communicate at an early age. They do talk in the videos and correlate the words to pictures, so they may also assist with speech. Here's the Web site: http://www.signingtime.com/
Early intervention is the most critical step, but even with that your son may not begin talking for quite some time. Our son began speech therapy at 2 years 10 months, but did not speak somewhat fluently until he was almost 5. And now at 6, he still is delayed with the language abilities of a 4-1/2 year old. By teaching your son sign language (and of course you need to learn it too) you may give your son the ability to communicate before he is able to formulate speech.
Best of luck! It's a long but rewarding journey to help a child that is unique.
Take care,
B.