Microsoft Windows 7 Release Candidate 1 will be made free for one year when it's released on May 5. If you are an MSDN or Technet subscriber, of course, you can already download the release candidate. The rest of us must wait until May 5 for the general public release.
EDIT: Link goes to MS Windows 7 home page.
This link on the MS Windows blog features the announcement:
http://windowsteamblog.com/blogs/windows7/archive/2009/04/24…