As we said they would a few weeks ago, Nvidia today showed off its line of Tegra chips designed for mobile Internet devices, becoming yet another entrant into the unproven market.

The Tegra chipsets are based on the APX2500 processor built for personal media players and navigation devices, but the Tegra target will be portable computers with screen sizes ranging from 4 to 12 inches. Pay close attention to news coming out of the Computex trade show in Taiwan this week, where more details should emerge from vendors using the Tegra chipset. Products based on Tegra will be out in time for the holiday season at the end of the year and cost about $200 to $250.

Also in the run-up to Computex, Intel’s CEO Paul Otellini told to the Financial Times his firm’s Atom chips (also aiming at MIDs) will chase $40 billion in market opportunities; Taiwanese computer vendor Asustek said it expected to double sales of it’s tiny Eee PCs in 2009 over this year. Even Dell is getting into the fray with a small computer. As products emerge, I’m eager to see how the market for the devices breaks down. Right now, the market opportunity is large because it’s ill-defined, with each vendor suggesting its own specs as the defining standard.

Will MIDs be small computers with voice as Otellini seems to think; phones with faster processing and media capabilities like Qualcomm, Apple and TI seem to envision; or will they be lightweight computers like the MacBook Air, Eee PC or what I bet the Dell effort is?