I take the concept of altruism with a giant grain of road salt. People want quid pro quo. For most donors, the altruistic reward is actually fairly far down the list. The trick is understanding what value they are assigning their volunteer effort.
Donors like being part of an effort, but it’s important to know what type of effort yields what type of reward, and to identify the people this will appeal to most.
Just a click away from thank you
Participation in a crowdsourced effort or simply encouraging your virtual customers to retweet and share your information is easy, but still makes you part of the herd, a powerful incentive. All those people who are copying your information to their networks are essentially volunteers. So don’t forget to thank them, and to let them know the impact their effort had (“Because of you, our Facebook following is now ###. Thanks for helping to make that happen”).
Special events
People who give to galas and other public events like access and recognition, which is why you see donor lists divided by level, and why organizations give freebies to famous people. But this does not work for every organization (see below, Celebrities) because access isn’t only access to a Name. It can be free entry to the pre-event, or early entry to your rummage sale, or a thank you dinner with the Executive Director. Understand what kind of access your donors want. Further, special events that segregate volunteers from the “real” donors drive me crazy. I’ve worked special events where they wouldn’t allow the volunteers to drink the WATER, let alone fed them. Get a donor to front the bill for full dinners for the volunteers, or see if the caterer will comp them. If you’ve got a volunteer who’s a lawyer in real life, and they just worked for you for 12 hours, that’s a $3,000 donation. Honor it. Feed the poor fools.
Celebrities
If your organization is glamorous, this will work. But if your donors are more workaday, they may not be impressed by or interested in that celebrity you’ve corralled, and the celeb is just costing you money (airfare, hotel, limo, etc.).
Insider info
Some volunteers like to know what’s going on, so be sure to give them lots of information– take them aside and do a brief orientation and pep talk, let them know where everything is, and who they can come to with problems. Watch for the petty dictators, but indulge them; find them a job where they can be in charge without stepping on people’s toes.
Recognition
Make sure people know who the volunteers are. They are often motivated by a desire to be in the inner circle, but not so inner that the outsiders can’t identify them. Give them a badge in a bright color; if it can be nicely designed or presented in a badge holder, even better. (These are expensive, so people don’t like to foot the bill. But a label on a bright piece of card stock works just as well.) Have extras, have blanks, so that people who lose them or last minute sign ups still get a badge.
Authority
A good volunteer effort will have both newbies and recidivists, um experienced helpers. Put the re-ups in charge of certain areas; have them show the newbies the ropes, and make sure people know who they are. Again, watch for the dictators, and make sure everyone understands that YOU have the final word on anything.
Just as in all fund appeals, you have to get the right message to the right people in the right way at the right time for the right return (are you seeing a theme here?) A poorly run volunteer effort is a nightmare. A good one will gain you friends for life.
Juno Consulting 
Segregating donors from volunteers gets my goat!
I went to a building open house. Major cash donors got access to a floor with catered food & drinks. Volunteers, many of whom spend hours each week at the facility, and have for 10 and 15 years on a regular basis, got bottles of water on a different floor. And guess where all of the senior staff, board members, and photographers were? It felt just awful.
I understand the need to do something for people who’ve given five- and six-figure gifts, but it would have been better to simply hold those events on different days.
I was a worker at the water-less event. When they told us we were not allowed to *be seen* consuming anything (including if we’d brought our own, just in case the “real” donors would think we were freeloading, which is how they put it) I left. This was a well-known, world famous cultural organization with an 8 figure income.