The Apple iPad has re-energized the market for tablet computers but it has gone nearly all of 2010 without a serious challenger. That's changing. Here's is my updated list of the top 20 upstarts that are taking aim at the iPad.
The best way to view this list is the companion slide show so that you can get a look at each of the tablets. Otherwise, you can get a quick summary in the list below. I've only featured tablets that have at least 7-inch screens and that have been officially announced (in most cases). The list also serves as a ranking. I've put the ones that are the most promising and the most likely to actually make it to market at the top of the list.
Based on a similar design to the Samsung Galaxy S smartphones, this 7-inch Android 2.2 tablet is loaded with strong specs and will be available on many different carriers, including all of the big four in the US. It is the iPad's most serious competitor to arrive in 2010.
Aimed at stopping the iPad's momentum with executives and business professionals, the 7-inch BlackBerry tablet will be built on its own QNX operating system and is flush with power with a 1 GHz dual core CPU and 1 GB of RAM. But, battery life could be an issue and the PlayBook won't arrive until 2011. RIM recently said the PlayBook will sell for under $500, which will make it a tempting enterprise device.
4. Cisco Cius
Primarily an enterprise communications and collaboration device, the Cisco Cius is an 7-inch Android tablet with a heavy layer of Cisco customization on top. Consumers won't be interested, but existing Cisco customers who want a corporate-controlled tablet might be.
2. HP Slate 500
Announced by Microsoft CEO Steve Ballmer at CES 2010 in January, this HP "Slate PC" running Windows 7 was intended to preempt Apple's iPad announcement later that month. It was reportedly canceled in mid-2010 when HP bought Palm and said it was going to create a webOS tablet instead. Then, the HP Slate 500 was revived this fall. HP recently admitted that demand for the Slate 500 has been stronger than the company anticipated.
One of the more innovative tablet competitors is the Libretto with its dual 7-inch multi-touch screens. One screen can be used entirely as a virtual keyboard while you work on the other. It runs Windows 7 acts a little more like a netbook than a tablet but it's an interesting concept.
This 10-inch tablet dual boots Windows 7 and Android 1.6. It has an LED display, 1 GB of RAM, a 1.66 GHz CPU, and a 16 GB onboard SSD drive.
7. ASUS Eee Pad
Now one of the world's top five computer makers and one of the leaders in design, ASUS has talked throughout the year about launching various iPad competitors (branded "Eee Pad") from 9-inch to 12-inch models, running Windows 7, Windows Embedded Compact, or Android. ASUS has promised a tablet will be coming in the first quarter of 2011.
One of the big hits of CES 2010, the IdeaPad U1 Hybrid is a convertible tablet with a multi-touch screen that detaches from a hardware keyboard. The main system runs Windows 7 but the detachable 11.6-inch screen turns into a standalone tablet running Linux. It has been delayed until 2011, but Lenovo says the standalone tablet will also be released separately as the Lenovo LePad.
9. Archos 10.1
Archos is a PDA and tablet company that has been trying to break into this market for a couple years with several different form factors and operating systems. The company could have a moderate success with its 10-inch tablet running Android 2.2
This 10-inch tablet runs on the Nvidia Tegra processor and Android 2.2. Unlike the Toshiba Libretto, this is a standard slate form factor. It's a vanilla tablet that Toshiba will try to price as low as possible.
We don't know much about this one other than it will run Android, have "high-end features," focus on productivity, and LG executive Chang Ma said "Our tablet will be better than the iPad."
12. MSI WindPad 100
This one is expected to come in both Windows 7 and Android versions. The Windows version has heavy specs with an Intel Atom processor, 2 GB of RAM, 2 USB ports, an HDMI port, and a 32 GB SSD drive.
13. Notion Ink Adam
One of the more intriguing iPad alternatives is the Adam from Notion Ink. It features a very slim, attractive design in a 10-inch tablet with a unique Pixel Qi display, Nvidia Tegra2, and Android 2.2.
14. NEC LifeTouch
This 7-inch Android 2.1 tablet is primarily aimed at accessing apps over the network and will be launched first in Japan. It will be sold to enterprises rather than consumers and NEC envisions it being used for health care, sales, and logistics work.
15. ExoPC Slate
This is a minimalistic tablet running Windows 7, an 11-inch display, and an Intel Atom processor. It has its own custom UI running on top of Windows and is focused primarily on multimedia.
16. Motion J3500
Motion has been on the most effective Tablet PC makers for niche industries, even as Microsoft let the Tablet PC platform languish in recent years. The J3500 is a ruggedized tablet that can run up to a Core i7 processor and Windows 7. It has both Microsoft's traditional pen technology as well as capacitive touchscreen. It's expensive but powerful.
17. Viliv X70 EX
The X70 EX looks less like the iPad and more like the Windows Ultra-Mobile PCs (UMPCs) of the past. It's a 7-inch tablet made to operate with two hands. It's a Windows + Intel device that is also made to easily mount in your car as a GPS.
18. EnTourage eDGe
Like the Toshiba Libretto, the enTourage eDGe features dual screens, but the eDGe has an e-ink e-reader on one side and an Android tablet OS on the other side.
19. Nefonie WeTab
This tablet (formerly called the "WePad") runs the MeeGo OS in an 11-inch form factor and is powered by an Intel Atom processor.
20. Augen Gentouch78
Also known as the "K-Mart tablet," the Gentouch78 is perhaps best known for its low price - $150. However, considering this Android tablet is barely functional, even 150 bucks might be too much to spend on this 7-incher.
Don't forget to check out the companion slide show, which provides a look at each of these tablets.
Jason Hiner is the Global Editor in Chief of TechRepublic and Global Long Form Editor of ZDNet. He is an award-winning journalist who writes about the people, products, and ideas that are revolutionizing the ways we live and work in the 21st century.