Company that specialized in wireless data networking. Their core product was the Ricochet "modem" and related service, which was deployed in ~15 major urban areas, and planned expansion to ~48 by the end of 2002. Their NASDAQ ticker symbol was MCOM.
The technology was quite cool, with a wireless modem the size of a cigarette pack that velcroed to a laptop, one could have high-speed Internet access from anywhere in a covered urban area. The last iteration, R2, provided speeds of 128 kbps, using a microcellular network infrastructure.
The company became defunct circa July 2, 2001. It seems that no matter how cool/nifty/elegant a technology is, if it's not marketed well, the company is doomed. Kind of depressing, that.
Given that Metricom is defunct and 3G hasn't panned out, here's hoping 802.11b will fill the void.