The Whitney has updated it's Whitney Biennial website, adding a bit of a disclaimer along with a submission deadline -
Please note that the Whitney Biennial is not a juried exhibition and, therefore, there is no formal submission process. If you choose to send materials, mail them to the address below by August 1, 2005. Submission packages should be limited to one resume/CV and six to eight images. Acceptable image formats include slides, computer printouts, digital files on CD_ROM (PC Compatible), audio CDs or VHS videotapes. Additional materials, including original artwork, portfolios and catalogues, will not be accepted. Please provide a self-addressed, stamped envelope if you would like your images returned. We are unable to answer individual inquiries regarding the status of a submission.
Whitney Museum of American Art
945 Madison Avenue
New York, NY 10021
The official 2006 Biennial website will be published later this year.
I hope they get a lot of submissions from artists all over. Previous posts on this are 12-06-04, 01-16-05, 01-28-05, and 02-05-05.