With the iPad still in its infancy, we've yet to see the full effect it may have on everything from computers to gaming consoles, from books to magazines and newspapers. One thing that is clear: Apple's newest device has inspired rival companies to ramp up development on their own versions. A concise guide:

How many other tablet PCs are being prepped?

15 to 20 slate computers designed to take direct aim at the iPad are in various stages of completion, says Danny Allen at PC World, including products from Hewlett-Packard, Dell, Nokia and Asus.

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Can any of them seriously rival the iPad?

The Dell and the Asus models have sparked interest among tech journalists. But the HP Slate, announced a few weeks before Steve Jobs revealed the iPad, has generated the most buzz — though nothing compared to the fevered speculation about the iPad.

How does the HP Slate compare to the iPad?

Quite well. Despite a slightly smaller screen (8.9 inches vs. iPad's 9.7-inch screen), the HP Slate reportedly includes some superior features: a slightly faster processor; an SDHC port to expand storage space; a SIM card slot, which enables the use of a 3G modem; USB port; audio and HDMI outputs to connect it to your high-definition television or computer monitor, and two cameras, one front-facing. By comparison, the iPad has no outputs, no cameras and no complimentary 3G capability (it can be built-in at added expense). The iPad, however, boasts better battery life: 10-12 hours versus the HP Slate's 5 hours.

Which operating system will the HP Slate run on?

Most likely, a touchscreen-enabled version of Windows 7. However, a version of the device that runs on Google's Android OS may be available.

How much will the HP Slate cost?

According to an internal HP memo, two models of the Slate will be released, one with 32GB of storage for $549, and a 64GB model for $599.

And when can I buy one?

HP hasn't yet announced a release date, but bloggers speculate that the 32GB model could hit stores by June, 2010.

Has HP ever made a touchscreen computer before?

Yes. In 2007, HP released the TouchSmart IQ770 touch screen desktop PC, igniting speculation over whether it had ushered in "a new generation of computers," says Antone Gonsalves in InformationWeek. At $1,800, however, it proved too pricey for most customers.

So, the iPad isn't the first touchscreen computer?

Not at all. Computers using a touchscreen interface have existed since the 1950s. The 1982 Pencept Penpad 200, the first PC offered for the consumer market, required users to weild a "pen" or stylus to input handwriting gestures in place of a keyboard. Many other touchscreen computers followed, most of which used a stylus, rather than a finger, to interact with the device. Apple's first, the 1993 Newton, sold poorly and is widely considered one of Apple's major failures.

Sources: PC World, Forbes, CNET (2), WSJ, Engadget, Device mag, InformationWeek, New Launches