ATI's Radeon X600 and X300 are going to be launched this week according to The Inquirer. The top end mainstream card is the Radeon X600XT with a 500MHz core and memory clocked at 740MHz DDR, it also has VIVO.
The Radeon X600PRO is a little bit slower, it is clocked at 400MHz and its memory at 600MHz DDR. It will be available with 128MB or 256MB RAM.
The X300 will be for the entry level market. It is going to be clocked at 325MHz, with 400MHz DDR memory using a 128 bit memory interface.
The Radeon X300SE uses similar clock speeds as the X300, but has only a 64 bit memory interface.