Krugle seems to be on a roll of late. Hot on the heels of their announcement about providing code search integrated into the Yahoo! Developer network, Krugle has now announced that they are working together with Microsoft.
In this new arrangement, Krugle has added to it's index the code from Microsoft's shared and open source initiatives. These initiatives, known as Microsoft CodePlex include more than 500 projects.
The addition of CodePlex expands upon the already rich variety of open source projects searchable by Krugle. As far as I know, no other search platform is able to search through CodePlex. Krugle also provides contextual search, so search results include reference information on the projects, and also can present source code in a context sensitve manner.