Lightroom 4 is now officially part of the Creative Cloud, which is Adobe’s bundled software subscription service. If you are a Cloud member, you can download it at no additional charge.

The Cloud gives you access to all of Creative Suite 6 (including Photoshop CS6), as well as additional services, such as cloud storage. Read more about the Cloud, and on weighing  Cloud subscription versus stand-alone purchase options, in this related post.