I read the other responses about your question and the range given 50-300 is appropiate for this age. It is hard to give ranges for speech development because it is a very indiviualized developmental acheviement. I would say not to worry to much about it unles your child seems to not notice you when you speak to them.
Children early on have a higher receptive vocabulary than expressive vocabulary so you might look for them to seemingly understand simple phrases or words, like "want your cup" or "where is daddy" etc. If your child has less than 25 words expressive or receptive at the age of 2 I would definately have them evaluated or if you just feel the need to. If it turns out that there is a speech delay you will be glad you caught it so soon because results of speech therapy are exponentially better the younger it is started.
A good place to look for services, more information, or a professional opinion is at Vandy. Specifically the Kennedy Center located on Peabody Campus, The Bill Wilkerson Center located in the Medical Research Building East Across from the ER, and the Child and Infant Developmental Labs located mostly in the Hobbs and Panye Buildings on the Peabody Campus. I'd suggest checking into services and studies at Vanderbilt University through this site:
http://www.mc.vanderbilt.edu/gcrc/volunteer.html
This site links you to most if not all the different studies going on. I have my son in a Hearing study as a control subject. All evaluation are free if you qualify for the study and some even copensate you for your time and gas. Well worth checking out.
Go Vandy! Hail to the Black and Gold! :-)