Here is some good information from the CDC.
Learn the Signs. Act Early. Important Milestones: By The End Of 2 Years-NCBDDD
Do keep in mind that there is a wide range of 'normal' though. But don't think twice about having him evaluated if you have any concerns. You can get him help if he does need it, or put your mind at ease if he doesn't. I had my son evaluated for speech at age two and while I was really concerned going in, I found out he didn't qualify and while at the low end, his speech development was normal. And it was my two early talkers that weren't 'normal.'
Good luck!