Update: A new list of popular iPad competitors can be found here.

Here are the iPad rivals that seem promising for tablet PC lovers this 2011.

Samsung Galaxy Tab
First in our list is the Samsung Galaxy Tab – deemed by many to be the hottest iPad alternative. Users can enjoy its built in rear and front cameras that many users are looking for in the iPad.
This ipad competitor has smaller size that proves it is more portable than the tablet PC from Apple. Additionally, the Samsung Galaxy Tab is capable of SMS and voice call turning it into a mobile phone.
HP Slate 500
With price starting at $799, the HP slate is perfect to those who prefer Windows® environment. Users can also enjoy applications for the Windows OS. Its 2 cameras also outlast the lack from the iPad rival. You can take photos and videos on he go as well as do video conferencing.
ipad competitor-hp slate 500

This ipad competitor can easily be turned into a conventional computer device with its flexibility of having USB 2.0 ports. Plug in mouse, keyboard, printer, etc – instant desktop computer!
BlackBerry PlayBook
ipad competitor-blackberry playbook
Another iPad competitor in our list is the PlayBook from BlackBerry. Its pretty small dimension of (130) x (194) x (10) hides a good computing power with its 1GHz Dual Core processor and 1GB RAM. It has the BlackBerry Tablet Operating System. It is also packed with other good attractions like its 5M rear and 3M front cameras.
Dell Streak

ipad competitor-dell streak
If you are looking for a more compact tablet PC, you might consider the versatile Dell Streak. It has 5-inch display – perfect for more personal viewing. This device is now available unlocked with Android 2.2 Froyo Operating System. For connectivity it has WLAN, Bluetooth®2 and USB 2.0 support. Additionally, it comes with a 5M front camera.
The JooJoo

ipad competitor-joojoo
For those who prefer Linux OS on their tablets, the JooJoo from Singapore is still a popular choice. This device runs on 1.6 GHz chip that overshadows the 1.0GHz of iPad. The 12-inch viewing screen is way bigger than the 9.7-inch of iPad.
Update (Feb 25, 2011):
This list has been updated. Please see:

Latest iPad Best Competitors for 2011 | New List and Comparison