Open Invention Network is the well known organization that acquires patents and bands companies together where they agree to not assert their own patents against Linux and other Linux/open-source projects. OIN is backed by companies like Red Hat, IBM, Sony, Novell, etc. Open Invention Network seeks to protect projects like the Linux kernel, Firefox, GIMP, MySQL, GIMP, Apache, and many others. X.Org Foundation has now joined the OIN ranks.
However, it's not particularly useful at this point since the X.Org Foundation itself holds no patents and it hasn't faced any significant legal threats or litigation. It's too bad though that S3TC or other interesting patents aren't part of the OIN pool. Regardless, nice move for the X.Org Foundation and some progress made by the board.
The Xorg OIN announcement was made at X.Org.