The internet: Precisely who 'invented' the mass of linked computer networks that is today's internet is a moot point. But it wouldn't have happened without the ARPANET network built by DARPA in the 1960s. The idea was to make a "self-healing" communications network that still worked when parts of it were destroyed. It was the first network to transmit data in discrete chunks, not constant streams, and led to the development of the TCP/IP specification still in use today.
GPS: We would be quite literally lost without today's global positioning system (GPS). But long before the current NAVSTAR GPS satellites were launched, came a constellation of just five DARPA satellites called Transit. First operational in 1960, they gave US Navy ships hourly location fixes as accurate as 200 metres.
Speech translation: Although not yet available to consumers, handheld language translation devices developed with DARPA funding are already being used in Iraq. Although accuracy can be as low as 50%, the devices have met with favourable reviews from forces on the ground.
Stealth Planes: It's probably the best example of DARPA fulfilling its remit to come up with "surprise" technologies - even the US Air Force was surprised by the idea. The first prototype, Have Blue, was tested in the late 1970s and became the precursor to F-117 Nighthawk stealth fighter.
Gallium Arsenide: One of DARPA's lesser known accomplishments, semiconductor gallium arsenide received a push from a $600-million computer research program in the mid-1980s. Although more costly than silicon, the material has become central to wireless communications chips in everything from cellphones to satellites, thanks to its high electron mobility, which lets it work at higher frequencies.