Now you can dictate your music playlist to your mood with Tune Your Mood by JSC Softkey. The program, developed exclusively for the Windows Phone 7, utilizes Internet radio to play songs. Unlike other programs, such as Pandora, it has over 100 mood and activity tags to set your listening mood to, so you have plenty of customization to help you through your day.
However, the current version seems a bit buggy, so waiting a few days could be beneficial.
You can get the app here for $0.99, including a free one month trial, or by scanning the tag below.