Free HDRI Studio packs

On www.deviantart.com you can get 3 HDRI Studio packs for free from user zbyg.
(in total 34 files)

More info and download:
HDRI Studio Pack 1 
HDRI Studio Pack 2 
HDRI Studio Pack 3

Edit: 
And there exists Highres version of some of the HDRI´s of the Studio packs downloadable on the 3dtotal forums.