Language delay

Our son is 2 and only says one word. He doesn't HAVE a vocabulary! :) He does know some sign, but doesn't use it much. We do work with an Early Intervention specialist as well as actively interact with him while talking (place his hand on our throat and lips, do exaggerated word formations, etc. as he shows interest). He has excellent receptive language, just not much expressive. He did have a rough start and a few months of hypertonia, reflux, and some seizures. Those have all mostly resolved -- he remains less flexible than many toddlers, needs antacids with meals, but no seizures in the last 1 1/2 years. I'm not overly concerned since he has had various delays, most of which are resolving, but am still keeping an active eye on how the speech is going -- or rather is NOT going. Any ideas? Web sites? Pointers for areas I might have not thought to check out? Thanks