The Boy Genius Report is saying that their sources at RIM have stated there's a new Blackberry tablet in the works.
The Blackberry tablet is rumored to be 8.9" and functionality should be on par with Apple's iPad which means it should be able to read email, browse the web, offer video playback and allow games. There is a possibility that the tablet will have access to Blackberry App World which may help expand the quality and number of apps currently available.
The tablet is being called a companion device for your current Blackberry hand-held. This means it won't have its own cellular connection but it will be capable of tethering using Bluetooth or a connection over WiFi.
Sources within RIM say the tablet is scheduled to be released in December but they hope to have it finished and shipping sooner than that. Originally the device was going to be a monochrome tablet, like the Kindle, until Apple came out with the iPad.
Boy Genius says this about the new Blackberry tablet, "To be honest, as a complementary device that is coming from RIM, we are not sure why they are even trying here. Especially since RIM employees have privately voiced their frustration to us regarding this initiative."