Nothing keeps me going mid-workout like loud, snarly guitars and fast, heavy drums. But for Billy at Beer Belly Blog, the “prevalent use of groove” and “trippy soundscapes” of techno/dance music are the main motivators. (“Listening to this playlist makes me feel like a 10 year old with ADD high on caffeine,” says Billy, who’s got “Jump” from Madonna’s Confessions On A Dance Floor on his iPod workout playlist. “I can do my cardio exercise forever.”)

To discover more of those prevalent grooves and trippy soundscapes, Billy uses Pandora, a free streaming radio service. Here’s how it works:

“Pandora has hundreds of attributes for all the songs in their database and basically match up these attributes to a song that you pick. When songs are selected for you, you have the choice to tell them whether you like it or not. And the longer you listen to Pandora and guide them towards your preference, the more accurate it becomes in picking out tunes that you love.”