This is straight from the Windows 7 Team Blog and posted the key section with the dates of availability.

Partners & OEMs: ISV (Independent software vendor) and IHV (Independent hardware vendor) Partners will be able to download Windows 7 RTM from Microsoft Connect or MSDN on August 6th.

Business Customers: If you are a Volume License (VL) customer with an existing Software Assurance (SA) license you will be able to download Windows 7 RTM in English starting August 7th via the Volume License Service Center (VLSC). The rest of the languages for Windows 7 RTM should be available within a couple of weeks after that.

IT Professionals: There are a few ways you can get Windows 7 RTM. IT Professionals with TechNet Subscriptions will be able to download Windows 7 RTM in English on August 6th and remaining languages by October 1st.

Developers: Developers with MSDN Subscriptions will be able to download Windows 7 RTM in English on August 6th and remaining languages by October 1st.

Beta Testers & Enthusiasts: A special thank you to our beta testers is needed for their time and effort in helping make Windows 7 a solid release. The special pre-order offer we did offering Windows 7 Home Premium and Windows 7 Professional at almost 50% discount was done with our beta testers in mind. And many of you jumped at the chance to take advantage of this deal – thank you!