AT&T launches BlackBerry 8820 with WiFi
Otherwise the 8820 and 8800 are identical, and the new model comes as replacement of the older. Currently it is offered for $299 with a two-year contract (after mail-in rebate), which was the price the 8800 was available for when it launched. The latter is now available only refurbished, for $149.
RIM BlackBerry 8820 Specifications