Dpreview has a hand-on preview:
In many respects the EOS 550D is a 'baby EOS 7D'. As well as getting a resolution boost to a class-leading 18 megapixels and a significantly upgraded movie mode (which now offers full HD capture at up to 30 fps, has full manual control and the option to use an external stereo microphone), the EOS 550D gets the 7D's sophisticated new metering system (bringing it a lot closer to similarly positioned Nikon SLRs). It also sports a new widescreen (3:2) LCD panel, has improved button design and finally offers the ability to customize the Auto ISO function.[UPDATE] This model also features a "Movie crop" mode, which records with the central 640×480 pixel area of the sensor, creating an effective magnification of approximately seven times.
When I first read about the movie crop mode, I had hoped that it would take the 18MP sensor, and crop it to HD (1920x1080), which would have been an interesting function (doing this would remove the need to rescale the captured image before compressing, and might have improved aliasing issues.)
A video from PhotoPlus magazine has a hands-on video that shows the Canon 550D (T2i)
It's up for pre-order at Amazon: Canon EOS Rebel T2i 18 MP CMOS APS-C Digital SLR Camera with 3.0-Inch LCD (Body Only)