I don't know very many people who ring up grocery purchases or manage corporations or law firms as a hobby,
Not a "law firm" exactly, but the prosecutor's office in Long Beach, California is looking for volunteers to prosecute criminals for free. This economy is rough.
Pro bono legal work (not in any way affiliated with U2) predates the current economic downturn.
If you have graphic design experience, check out the on-going logo design competition at 99designs for the Singularity Institute. There are still 6 days left to enter and be eligible to win the $295 prize if your design is selected. Tell your friends with graphic design experience too. There are very few submissions currently.
Note: This is a blind contest. Designers can only see their own entries. All designs will be revealed when the contest ends.
If you're interested at getting a peek at the designs, they will be online after the competition is over. This is standard practice in 99designs contests to prevent designers from contaminating each other and having all the designs drift in a certain direction.