Apple has closed its online stores (US [1], DE [2], FR [3], UK [4]...), as it is usually the case before a new product release.
New PowerMacs are expected [5] to be released today. Yesterday, Amazon.com has prematurely [6] started taking orders [7] on the new PowerMac family and, by the way, revealed their technical specifications.
Stay tuned as we'll be updating when there is something new.
UPDATE: New PowerMac have been released, more here [8].
Links:
[1] http://store.apple.com/1-800-MY-APPLE/WebObjects/AppleStore
[2] http://store.apple.com/Apple/WebObjects/germanstore/
[3] http://store.apple.com/Apple/WebObjects/francestore/
[4] http://store.apple.com/Apple/WebObjects/ukstore
[5] http://www.macosxrumors.com/articles/2005/04/25/what-can-we-expect-this-week/
[6] http://www.macosxrumors.com/articles/2005/04/26/amazon-reveals-new-powermacs-specifications/
[7] http://www.amazon.com/exec/obidos/redirect?tag=macosxrumorsc-20&creative=9325&camp=1789&link_code=ur2&path=tg/browse/-/541966/ref=amb_center-3_186341_38
[8] http://www.macosxrumors.com/articles/2005/04/27/apple-releases-new-powermacs/