While Apple is planning to offer a music stream service for iOS Devices soon in future, DropTunes a project of DropBox come up with the facility to stream music on your iPhone, iPad and iPod Touch. DropTunes a completely free service, which works on DropBox accounts. To stream music on your device you just have to upload your audio to the DropBox account and then you have to visit the DropTunes website from your iOS Device and give credentials of your account, where you already have upload the music.
The entire page of DropTunes is flash based, but they already designed a HTML 5 page for iOS Devices just select the HTML 5 option and enjoy their service.
To listen to music, just click the Play to the left of the title and then the play button above. This double pass allows you to load in memory of our playlist.