A nice slideshow of computer related images on stamps, circa 2005 can be seen accompanying a story about topical stamp collector Larry Dodson at Business Week.
How much has changed since that article six years ago? Well, apparently Mr. Dodson wasn't just putting together a computer stamp collection, but also an American Topical Association handbook that is currently very, you know, topical: A Philatelic Tour of the American Civil War. He also authored a book called The Philatelic Adventures of Sherlock Holmes. And of course he has philatelic computers and related pretty well covered in Computers on Stamps and Stationery I and II.
You may want to check out membership at the ATA, as they are having an incentive promotion where new members receive two free handbooks, including the classic Adventures in Topical Stamp Collecting by Griffenhagen and Husak and another selection from many handbooks available.