We can check the official sites one by one each time for the latest Sigma Art's, Tokina's, Canon's... but is there an independant site that publishes this news or has maybe great reviews ?
In past I checked Fredmiranda, but this one isn't always up to date.
Also The Digital Picture, Steve's digicam's, Dpreview.
Now and then I check the movies on Digitalrev.
Maybe the most up to date site which also has a mobile friendly app ?