NVIDIA and AMD announce new GTX 275 and HD 4890 accelerators. There are articles comparing the two new products on HEXUS.net, Legit Reviews, and PC Games Hardware, and here's word on each card:

NVIDIA GeForce GTX 275
NVIDIA Extends Performance Lead With New GeForce GTX 275 GPU announces new GeForce GTX 275 graphics accelerators from NVIDIA, which will be available starting April 14. The new cards will occupy a price and performance point between the GTX 260 and GTX 285, as suggested by the naming convention. Word is: "Based on the GT200 architecture, the GeForce GTX 275 GPU features 240 processor cores operating at 1404 MHz, 80 texture processing units, a 448-bit memory interface, and an 896 MB framebuffer." There are reviews on Bjorn3d, Hardware Canucks, HotHardware, Ninjalane, Overclockers Club, and techPowerUp.

ATI Radeon HD 4890
ATI Radeon™ HD 4890 Overview has word on AMD's newest graphics accelerators, though details like pricing and availability are not included. Word is: "The newest addition to the award-winning ATI Radeon™ HD 4000 series boasts a whopping 1.36 TeraFLOPs of compute power, superior GDDR5 memory, and super-high engine clock speeds capable of nearly 1GHz." The new cards are reviewed on AMDzone, Bjorn3d, Benchmark Reviews, Elite Bastards, Guru3D, Hardware Canucks, HotHardware, InsideHW, Neoseeker, Overclock3D.Net, Overclockers Club, PC Perspective, techPowerUp, techPowerUp (Crossfire), TweakTown, and X-bit labs.