Slacker: Slacker is a really slick internet radio website and app platform available on most smart phones. Slacker used to be in the hardware business and has always had two tiers of subscription: free and premium. On iOS devices that difference between the two tiers is largely mitigated if you have an iPhone with unlimited data. But, if you have an iTouch or a data limited plan from AT&T, the premium tier really begins to make its $5.00 per moth charge worth it. This is because the Slacker app will cache your music using any available space left on your iOS device meaning for on five big ones per month, you get a boat load of music you can listen to anytime and without net connectivity. Slacker's ease of customization and myriad of stations means you can get the exact type of music you want. Just remember that if you use their free tier, you will have to listen to commercials and be limited to six skips per stations per hour.
Pandora: The classic poster child of internet streaming radio Pandora has long ruled the roost. We love Pandora's algorithms that match music you like based off of a particular artist you like. It has helped us come to find new artist and rediscover old ones we had long since forgotten. Like Slacker, Pandora has a premium service that is $36.00 per year with no ads. But unlike Slacker, it does not offer station cacheing so network connectivity is a must. If you are a metropolitan dweller, Pandora is a commuters dream and seems to keep us happy whenever we turn it on in the car.
Rdio: Rdio is a very different service from Slacker and Pandora. It is built with the intent to network and help you discover and listen to music in a very social media way. Using it purely as an adaptive online radio station is not its intent like Slacker and Pandora. It took us a while to adapt to the list and other social features of using Rdio and that is essentially lets you adds tracks in an online media library. Once our expectations were recalibrated we loved that Rdio also had an offline sync feature and could essentially replace our media library in iTunes. The downside is that it costs $10.00 dollars per month and cannot be used for free. Bottom Line: We love Slacker and the old school radio style that lets us choose from professionally made stations. Slacker also acts as a great compliment to our current iTunes library for the same reasons we love Pandora as well. Both work well with the style of listening we have. Rdio is an incredible option if you love the power and versatility of not buying music and having a very social music experience. Our only personal issue is our large iTunes library and the desire to own our music. But, if you're a harddrive starved music junky and want the best of streaming, cached, and socail music, give Rdio a try. Update: Slacker will soon be rolling out Slacker Premium with On Demand that has capabilities very similar to Rdio and will allow music storage and playback. Correction: It was previously stated in error that Slacker only allows 6 song skips per day, this has been changed to reflect that Slacker allows 6 song skips per hour.