Scott Underwood, former IDEO jack-of-all-trades, has a wonderful history of the IDEO's ubiquitous logo in his portfolio of projects from his IDEO days. Read the full story here.
Steve Jobs (who made news today) recommended the graphic designer who designed the first logo, Paul Rand. At the time, in 1991, IDEO couldn't afford Rand's rate for a complete corporate identity, and so Rand only designed the logo. Bill Moggridge had come up with "IDEO" after finding the root "ideo-" in the dictionary. However, people often asked what I-D-E-O stood for. Early acronyms, like "an innovation design and engineering organization," came only after the fact and never caught on.
In 1997, the logo was altered slightly by Pentagram's Michael Beirut. The I, D, E, and O were thickened and reshaped to fill the blocks more evenly. There was even a Google-esque primary-color version, two years prior to the introduction of Google's now-iconic logo.
Each of the various departments within IDEO were allowed to choose their own color scheme for business cards, while each employee could choose one of the logo variations. This great idea granted a bit of individuality within a uniform corporate design.
Other logos—many short-lived—were also designed over the years for various IDEO ventures.