140+ Slick Icons In .Design & .PNG – WP7 Icons
WP7 Icons is a growing collection of free icons that are mono colored (black and white versions are available).
They are in transparent PNG + vector .Design (for Expression Design) formats and the PNG version is sized as 48*48px (or 24*24px once the empty space is trimmed).
The set includes items from add or delete to media controls and social networking icons.
P.S. The designer also provides a tutorial on "how to create such icons using Expression Design.