Microsoft has given the open-source community a belated Valentine's Day present by adding its Office file formats (.xls, .doc, and .ppt) to the Open Specification Promise. It also added information on patent/copyright coverage and information on how OSP interacts with GPL-based software development. (You can see what the site looked like before the changes using the Wayback Machine.)
Good for you, Microsoft.
No, Microsoft wasn't motivated by peace, love, and Linux. Rather, the contribution of the binaries is focused on getting OOXML approved:
The binaries were published in response to concerns among national bodies voting whether or not to ratify OOXML as an International Organization for Standardization (ISO) standard, according to Microsoft Office program manager Brian Jones. The national bodies were concerned that third-party developers may have had difficulties converting Office binary formats to OOXML, referred to in the ISO ratification process as "DIS 29500".
I haven't looked at the specifications, but there are complaints that they're incomplete. I'm sure Microsoft will drag its feet as long as it can on a full release of the specifications. The goal is OOXML approval, not to allow anyone to cut into its Office monopoly.
Still, a start is a start. Let's hope it continues.