Some good websites on autism and similar pdds can be found on www.childbrain.com/pddassess.html, www.braintalk.org, and info.med.yale.edu/chldstdy/autism. I also have address of groups.yahoo.com/group/Latetalkers regarding delayed speech communication but haven't checked it out yet. Sorry if any of the above repeats this group; I'm an American ex-pat living in Germany trying to find more info for my 19-month-old son and sometimes get confused with my research!
Accurate diagnosis at this young age can be difficult. If he seems to have a desire to relate to people and has some social behaviors, it's not likely that he displays any severe form of autistic-spectrum disorder. But, there is a wide variety along this spectrum and often we need to observe carefully as children develop before their status really becomes clear. The diagnostic task is even more difficult with children who display some form(s) of neurointegrative disorder, like SID. On the home front, try to engage with him in a normal fashion. Keep communicating verbally with him, and try to stay away from gestural communication or any form of communication that de-emphasizes his reliance on words. When he starts his OT, the therapist may well have some exercises or games that you can use at home to help him develop. For now, though, there's no need to be worried about that. He's getting some help at a young age, and that's what's important.