Don't forget that board members are volunteers as well, and probably the most important ones in an organization. Put some thought into attracting and retaining the right ones. Don't just invite individuals with money and connections, but aren't willing to invest the time into your organization.
Local corporations are a great source of board members and volunteers.
Here's some interesting volunteer resources on the Web. Very sophisticated site with a virtual volunteers category. Idealist A project of Action Without Borders. Post your volunteer opportunity online. Some virtual volunteering opportunities.