For a short time, I've got an office at work. I've started framing some of the original comic art that I've gotten, and putting it up. Buying this type of art is a good way to support cartoonists you like, of course.
The great Rob Ullman, who illustrated the sex column for the Washington City Paper for years, did the above. As a spot illustration, this doesn't have a title, but I call it "Coffee I.V." He's got a new minicomic for sale.
"Dr. Jenner's Vaccine" original scratchboard art by Baltimore children's book artist Jeff Thompson (of Big Planet Comics) on vaccinating for smallpox with cowpox. You can buy his art here.
"Penicillin" original art by British cartoonist Hunt Emerson, - a Christmas gift from my wife. You can buy his work here.