Charles Petzold has created a Windows Phone 7 program that allows recording short vocal memos.
Source: MSDN Magazine
At first, I thought it would be fine to have just two buttons labeled Record and Play, both of which functioned as toggles. Press the Record button to start recording and press it again to stop. The program saves the audio data in isolated storage. Press the Play button to play it back. Each press of the Record button replaces the previous memo so the program doesn’t need a Delete button.