There's very little that's different between the Sony Cyber-shot DSC-T90 and the DSC-T900. The T90 has a 0.5-inch smaller screen that has a significantly lower resolution (910K to 230K dots). It also doesn't have a stereo mic or have HD output via HDMI, only component. But, that's pretty much where the feature shed ends.
Basic specs for the ultracompact include a 12-megapixel sensor, 4X optical zoom with stabilization, 3.0-inch LCD, and 720p HD movie recording. You also get Sony's intelligent scene recognition, intelligent auto mode, Smile Shutter, and face detection with child and adult priority.
The T90 model is available in silver, black, pink, blue, and bronze for about $280.