Allow taxpayers who volunteer their time with 501(C)3 organizations to deduct their time at a rate commensurate with their income, up to 5% of their total income. This will encourage more people to volunteer their time. Once directly involved, they will likely become engaged and encourage others to do so as well. This builds community.
This will encourage both low and high income volunteers. Organizations would greatly benefit both from the increased number of volunteers and from the high level skills and associations higher income volunteers would introduce.
No need to create an expensive system for verification. Simply publish what people claim they have volunteered. Watchdog groups will develop to seek out, expose, and punish cheaters.