The Nikon D5100 has been officially announced. Price with kit lens is $899.95. Most of the features, including 16 megapixel resolution, full HD 1080p video, side-mounted swivel LCD were as predicted by sites such as Nikon Rumors. The fabled "Night Vision Mode" with 102400 ISO didn't materialize however.
I find the built-in HDR feature interesting. It seems to work like the iPhone 4, taking two exposures and combining them. Hopefully it's faster at processing the HDR photos than the iPhone 4.
It's not clear yet whether the built-in flash can act as a commander, like the Canon 600D. On one hand the official brochure states only: "Advanced Wireless Lighting supported with SB-900, SB-800, or SB-700 as master flash, or SU-800 as commander." On the other hand, Digital Photography Review lists in the specs that: "Advanced Wireless Lighting supported with built-in flash, SB-900, SB-800, SB-700 or SU-800 as commander and SB-900, SB-800, SB-700, SB-600 or SB-R200 as remotes."