We're doing the same thing in a few weeks and did the same thing only three years ago when we moved here. Here is what I did:
1) google mom's group and special needs and the name of your new town -- I have found many SN groups for moms of children with SN in our new area
2) go on yahoogroups and do the same. This is how I found MCNeeds and also this forum.
3) go on the national listservs for your child's issues and search that way -- for example, DS has apraxia, so I went onto the New England group for apraxia and asked there for people who will live in our town in MA
4) do a google search for special needs support and the name of your new school district - again, I found (in our new place) a listserv for parents of kids with SN enrolled in our district
5) find the autism group for your new area. Even if your child doesn't have autism, the autism groups tend to be really organized and they can point you in the right direction. I joined one for New England even though DS doesn't have autism, and from posting on there, got names of therapists, doctors, you name it. DS has many issues that also are common with kids with autism, so reading the listserv daily has been very helpful as well
6) post here for info on where you're moving. I did this back this winter and got a couple of responses from people who had moved to DC from our new city, and they had great advice as well.
Moving with a child with SN is hard. I am so envious of people who just go to a new place and enroll their children in the local elementary school or the nearest preschool. On the other hand, we found when we moved here and now when we are moving again that moms of kids with SN tend to be extra welcoming and helpful, so we are finding it easy for me to make connections in our new place.
Good luck!