What a great question. And one that was proposed to me recently. I started thinking about the great nonprofit professional groups in San Diego, and here is what I came up with. Please comment or email with additional local groups!
YNPN San Diego: Great networking group that was started by these two gals: Emily Davis and Heather Carpenter. I highly recommend signing up for their listserve that sends out daily information on job postings, events and volunteer opportunities (http://ynpnsandiego.org/listserv.html).
Association of Fundraising Professionals aka AFP San Diego: Great group of fundraisers who meet monthly for a chapter luncheon and guest speaker. There are often monthly workshops, an annual conference and of course, National Philanthropy Day!
Stay Classy San Diego: The slogan endeared to Diegans by Ron Burgundy has formed an incredible group that does online social fundraising — especially cool events.