From Wikipedia :
With the release of the Creative Suite 3, ImageReady has officially been discontinued, and the expected reason is that since Adobe now owns Fireworks (the ex-Macromedia equivalent of ImageReady, and a more mature and arguably superior product), they don't need ImageReady, and will continue to develop Fireworks instead. There is some ImageReady-style functionality in CS3 found via File > Save For Web & Devices