Pro bono publica, most frequently shortened to pro bono means to work for free. The actual meaning of this Latin phrase is "for the public good" and generally refers to work done voluntarily without payment. Although often associated with lawyers, any kind of professional can volunteer to provide services pro bono, including graphic designers. Typically pro bono work is done for organizations or individuals who might not be able to afford such services normally and is often undertaken as a feel good activity. However, some designers may offer limited pro bono services as a means of getting experience, building a portfolio, or with the underlying notion that it could lead to future paid work.
There are right and wrong ways to do pro bono graphic design or Web design work.
Read about the two main rules for Doing Pro Bono Right


I do pro bono work, both as a designer and a photographer (though never wedding photography). That is, there is no monetary cost, but there is always a pay off. My advice is this
a) set aside a time for doing pro bono work. You client doesn’t understand how much money your time is worth, and without this, will use up good paying hours. Tell them something like, “I set aside Friday afternoon for pro bono work, expect my call then.”
b) Take their maney if they offer and establish a contract/specification. This is especially true of photography, but applies to design as well. Otherwise you’ll do the desin, then the print brokering, then the invites to the book launch, and so on it goes.
Never think “if once I worked pro bono for this organization, now they have funds and are willing to pay for the same job they will hire me instead of someone else”. Well, it might happen, but it never happened to me.
I think that doing pro bono work is potentially a great way to gain paying clients. Of course, I never expect that the organization will pay for future jobs. But many organizations have wealthy donors, and may have fundraising events that you could be invited to. Doing good work for you community is nice, plus the added benefit of networking!