Quietly, several high-tech companies are lining up to deliver versions of these keyboard-free, touch-screen portable machines in the next few months. Tablets have been around in various forms for two decades, thus far delivering little other than memorable failure. Nonetheless, the new batch of devices has gripped the imagination of tech executives, bloggers and gadget hounds, who are projecting their wildest dreams onto these literal blank slates.

In these visions, tablets will save the newspaper and book publishing industries, present another way to watch television and movies, play video games, and offer a visually rich way to enjoy the Web and the expanding world of mobile applications.

Tablet computers were first conceived as a way to supplant plain old paper, in the same way that PCs replaced the typewriter.

The drumbeat of tablet product introductions has already begun. In June, Archos, a French consumer electronics company, began selling a small touch-screen tablet running Google’s Android software. Later this month, it will introduce another tablet that runs on Microsoft’s Windows 7, which has built-in support for touch screens.

The industry blog TechCrunch has also commissioned its own Web tablet, called the CrunchPad, which it has said it will start selling later this year. Despite its past bruises in the tablet business, Microsoft appears ready to try again. In September, images of a booklike Microsoft device called Courier, with two 7-inch color screens, surfaced on Gizmodo. Apple’s rumored tablet is the most highly anticipated of the lot. Analysts expect Apple to introduce it early next year — a sort of expanded, souped-up version of the iPod Touch, priced at around $700.

Last week, Apple rehired the original chief marketer of its old Newton, Michael Tchao, who was working at Nike.  Tchao’s former Apple colleagues believe he will help market this new device. Apple’s tablet will most likely have little in common with the Newton, which was essentially a personal digital assistant. The new crop of tablets is being viewed as more flexible — gadgets that combine elements of the iPhone, e-book readers like the Kindle and laptops. Apple has been working on such a Swiss Army knife tablet since at least 2003, according to several former employees. One prototype, developed in 2003, used PowerPC microchips made by IBM, which were so power-hungry that they quickly drained the battery.

Despite the preponderance of apps, there is still the persistent question of whether regular people will really find a use for tablet computers. Smaller cellphones are increasingly multipurpose and fit nicely in a jacket pocket. And low-end laptops are inexpensive, run a full-fledged operating system and offer the luxury of a keyboard.