A Pack I know of has done the following. They would have a non-BSA adult evening. This would happen usually in September. They would meet at someone's home, barbeque, have the option of adult beverages, and play card games or board games (Queen of Hearts, Pictionary, etc). There was no or little mention of scouting. It was a method of getting to know one another in a pleasant social gathering. Later on in the year, when folks were contacted to assist or help with a project, they were not strangers to each other. Contact and communication went more smoothly. Also, there had been the opportunity to possibly discover strengths and/or over-views of each other (single parent/ has a 15 seat van, etc).
This didn't solve all their volunteer problems. But, they said that it did make it easier to recruit "new" help.