Model B - $35 - 256 MB Ram with 10/100 wired Ethernet
Model A - $25 - 128 MB Ram, No Ethernet
(WiFi via USB dongle)
The exact release date has not yet been confirmed, however, you can sign up for a notification email.
Join the Raspberry Pi Mailing List.
The 45g computer has a Linux based operating system which receives power via a 5volt micro USB but can also be powered with 4 x AA batteries. Features include:
- RCA Video
- 3.5mm Audio Jack
- USB 2 slot
- SD Card slot
- Ethernet (model B only)
- 85.60mm x 53.98mm x 17mm approx
The computer like the Mac Mini is soley a computer with no external devices.
To use connect the Raspberry Pi to an analog, digital TVor DVI monitor then via a USB hub add a keyboard, mouse, external storage, network device, WiFi Dongle, speakers etc.
Source and More Information: Faqs about Raspberrry Pi
UPDATE - 3 June 2013 & 4 June 2013 :
Need help setting up your Raspberry Pi - New Out Of Box Software (NOOBS) makes it a whole lot easier.