Dell, HP, and Lenovo are rushing to compete against the Apple iPad in the tablet PC market, which could reach 50 million units by 2015. We look at what's on offer.

The re-emergence of the tablet PC is one of the biggest technology stories of the year so far, largely due to the announcement and release of the Apple iPad.

On April 3, the first day of sales in the US, Apple sold 300,000 iPad tablets to eager buyers. However, just two weeks later it revealed it was delaying the UK and international launch of the device because it couldn't keep up with domestic demand.

But Apple's competitors are gearing up to ride the wave by prepping their own tablet PCs. Rivals to the iPad include tablets that run Google's Android operating system, Flash video, multitouch screens, front-facing cameras, and multitasking support.

These models offer alternatives to the iPad, which lacks key features such as Adobe's multimedia Flash technology, a camera, and a built-in USB port.

Will tablets become the go-to-gadget when you want to kick back and browse the web, check email, read an e-book or magazine, play games, or watch a movie?

Tablets have tanked in the past. Yet IDC, a market research firm, projects that the category of media-centric tablets may sell as many as 15 million units in 2011.

Analyst Bob O'Donnell of IDC says that Apple rivals will struggle to match the iPad's slick touch interface, unique content (such as iBooks and iTunes), and thousands of App Store applications.

"Success is pinned on the amount of apps you can offer tablet users," O'Donnell says.

But what iPad alternatives lack in apps they make up for in hardware specs. They will offer a broader choice of shapes and sizes, along with webcams (for video chat), USB slots, and HDMI ports.

Some upcoming tablets will pair Windows 7 with an Intel Atom processor, or match nVidia's Tegra 2 chip with Linux or Google's Android OS. Multitasking? Check. Flash video? You bet.

Google is said to be building a tablet that will run either its Android platform or the web-centric Chrome OS.

Microsoft may be developing a paperback-size dual-screen device, dubbed the Courier that may be more of a pen and touch-controlled digital journal/eReader than an iPad-style media tablet.

Meanwhile, Toshiba and Asus will hedge their bets by building both Google- and Windows 7-based tablets.

Toshiba has its eye on late 2010, while Asus is likely to unveil new devices (perhaps even a Chrome OS slate) this June at Computex - Asia's largest tech show.

Apple has done the tablet market a favour, according to Jeff Orr of ABI Research.

He believes that the iPad has raised the public profile of the media tablet category.

By 2015, ABI Research estimates, 57 million tablets will be sold annually. Here's a look at some of the tablets, besides the iPad, that may be popular in the year ahead.

NEXT PAGE: HP's Slate PC and other rivals

  1. We look at the offerings from other tech firms
  2. HP's Slate PC and other rivals
  3. Netbook tablets