BuildOn is a great way to volunteer you time and services to those in need doing just about anything. What I learned from volunteering is that even though you don't get money you do give hope and care to those you helped out and that does feel really good, no lie.
The people I volunteered with (Classmates) were fun to be around and made even boring projects fun and we always had good laughs.
The only hard part about volunteering to me is finding your way to the sites, but an easy google maps search will do the trick.
The most fun I had at BuildOn was fundraising for charity, you could sell just about anything as long you know people will buy it. Its all for a good cause, building schools in developing countries.