For insurance, we use Oberg in Bridgton. They've been great to work with, and even found us a better policy for less money than the one we had had through them before, without our even asking if they could do better.
As for keeping the member list current, I agree that town tax records often lag behind. Our membership has increased from 35 to 55 within the last ten years due to lots being subdivided, and also a number of lots have changed hands - some of them several times. It has been a challenge keeping up with the changes. A couple of times a year I go to the County Registry of Deeds website and do a search for each name. Each county' site is different, so I can't tell you what you can do on our county's site without knowing what county you are in. But in Cumberland County you can do an advanced search that lets you specify the town, a date range, and what kinds of documents. (If you get too specific, you may get zero results, but specifying the town is really helpful.) Then you can also click at the top of the date column in the list of documents under that name, and it will sort the documents by date. That makes it easy to see if there has been any recent sale of properties listed under that name. If you happen to have a member who is a land dealer, you may still have to look at the deed itself to see if the property that was sold is within your road association or not, but it does narrow down the number of deeds you have to look at.
The deed usually gives a mailing address for the person to whom the lot was sold, so I add that to our records. Then when we send out the notice of the Annual Meeting, I include a letter to the new people, welcoming them to the neighborhood. The letter also makes sure they are aware that the road is not plowed or maintained by the Town, and that these services are provided by the road association, which obtains funding for that purpose through member dues. If their deed mentions a requirement to become a member of the road association, I point that out to them. I also provide a link to the road association statutes, 23 MRS 3101 - 3104.
This process has become somewhat easier since the passage of the amendment to 33 MRS 173 and 193, which now require a disclosure in real estate transactions if the property being sold is accessed by a road that is not maintained by the public. This has resulted in most real estate brokers getting in touch with us to ask about details of the road association when they are about to sell a property. Unfortunately if it is a private sale, this doesn't always happen.