UK Maker blog:

Its been know that several updates have been in the works for Arduino, however the changes have gone further than many expected. arduino has now got a completely new branding package, including logos and designs that are now on the boards themselves and provide the theme for the shiny new website.
The hardware has also been updated, here is the new Arduino Uno (replacing the duemilanove);



the main difference in terms of hardware is the new usb interface, a Atmega8U2 chip is now used to handle the usb interface it will also now show up as "arduino" on your pc rather than popping up as a com port. I believe changes to the arduino programing environment or to follow shortly. regardless its great to see Arduino progressing in a positive was as it becomes ever more popular.