If you need some pep during a particularly long ass work day, listen to Slacker Radio.
Basic service is free, no installation required, listen using your Web Browser of choice (I prefer Mozilla).
My favourite station is 80s alternative. It reminds me of my childhood days back in the Philippines when I was between 4 yrs old to 11 yrs old and really into The Cure, Psychedlic Furs, Tears for Fears, etc.