My favorite is Berrytunes...not free (about $19 after discounts usually available). It's been the most stable of the radio apps I've tried in terms of providing a consistent stream w/out hiccups/skips.
One plus is that it includes both internet radio and podcast streaming (you can also download podcasts if you prefer). I listen to a lot of podcasts so that podcast support is an important addition for me.
It comes with a bunch of radio stations/podcasts pre-configured, and you can also add additional stations/podcasts. BerryTunes 2.5
It has a free one week trial.