I just found an app called boom box. It is free and you can just search a song and it will play it even if you dont own it. You have to be conected to wifi tho but im in Minneapolis so there is city wide wifi so i always have wifi.
acutally i think the best app recent, is Clippy which can be downloaded via cydia. It is real copy and paste added to the iphone keyboard. It works currently with apple apps, safari, notes, sms, mail. etc. check it out. works like a charm.
city wide being anywhere with in the city limits if you pay for it every month you can get wifi. So like you could be in rthe middle of a giant park and get it