The IRS values volunteers time at $20.85 per hour.  You can do the math for your most loyal and active volunteers but I bet the value of the time they contribute might exceed their financial donation.  If we looked at the budget impact of volunteers time by recognizing the expense of hiring a staff position and then adjusted the revenue to recognize the volunteer contribution I believe the total would overshadow many other programs.  Just for demonstration purposes, do the following quick calculations:

Number of board member  x  number board meetings x  average duration of meetings in hours  x  $20.85= IRS valuation of volunteer time

This equation does not take into account the committee meetings, fundraising events, task forces, and all the other volunteer responsibilities that your board members assume.  This is just one segment of the volunteer impact on the organization that is easy to quantify. 

A trend in annual reports is to list volunteers as prominently and appreciatively as the contributors.  Other initiatives include creating online forums where volunteers can connect with one another, sending special volunteer newsletters, holding meaningful recognition events hosted by donors and staff, seating volunteers at fundraising galas as invited guests.  Most importantly, the best volunteer programs ask each individual what talent they are most excited to contribute before providing them with a portfolio of opportunities.