Some of the world's biggest electronics companies are readying an assault on the tablet market. But before they even begin, they find themselves at an early disadvantage.

Though Samsung, LG Electronics, Acer, Hewlett-Packard, Asus, Research In Motion, and Dell have announced or hinted at touchscreen tablets that will arrive between now and March 2011, they're way late to the party. Since the iPad's debut in April, Apple has built a huge lead in this category--in terms of actual devices sold but also in many consumers' minds.

Samsung's upcoming Galaxy Tab tablet.

(Credit: CNET TV)

The category is new--a large touch-screen device bigger than a smartphone and running a lightweight operating system wasn't widely available to consumers prior to the iPad's introduction--but Apple got out of the gate and hasn't looked back. The company is selling about 1 million iPads per month and has not noticeably slackened its pace since.

The entire media tablet market is estimated to generate sales of just more than 12 million units by the end of 2010 and 25 million by the end of 2011, according to analyst firm IDC. Apple had sold more than 3 million by the end of June, and at that pace, Apple has likely sold about 4 million to date. That's almost a third of IDC's forecast for the year, and the all-important holiday shopping season is still ahead. So where exactly does that leave the latecomers?

At first glance, the chances of the Galaxy Tablet from Samsung or a WebOS-based slate from HP wresting some reasonable share of this market from Apple in the short term don't seem great. The companies with the most resources and brand recognition in position to compete with Apple are either only just getting their products into stores (see the Dell Streak) or about to put them into production (see the rest.)