Technically, Microsoft does not issue a project management certification such as the PMP, but it offers the "Microsoft Certified IT Professional (MCITP)" which encapsulates some project management in it, specifically the following tests:
- 70-6322, 70-6332, 70-6342 under the "Enterprise Project Management with Microsoft Office Project Server 2007" of this certification and...
- 70-667, 70-668 under "SharePoint Administrator 2010"
Again, technically, it's not purely a project management certification, but you do learn a lot about project management if you take these tests.
The MCITP is taken seriously by all companies, as with any Microsoft certification.