I have Bridge (and also Bolt App), but I'm using those mainly to bring in ringtones/alerts. I keep all my music in my iTunes library on my Mac, but I also have the Google Music Manager which uploads direct to Google Music (or Play, or whatever they are calling it now). I use an app called gMusic which allows me to directly access my entire iTunes library that's up there in Google Music and stream it to my device. The music controls for the iPhone work with gMusic so I can control it just like if I had actual music on my iPhone. There's even a music tweak on Cydia that allows me to control playback via my volume buttons which because gMusic works with the standard iPhone music controls means this tweak can control gMusic. All of this to me is great because I get access to my entire iTunes library, but zero of it is stored on my iPhone - so none of it takes up any storage space. Of course I need a WiFi or cellular connection to stream, but there is no shortage of either in the places I tend to be at.
Or as an alternative to a safari tweak you can use the Dolphin Browser from the app store which has the ability to download anything from the Internet. Just throwing it out there. There are free alternatives to bridge as well. You can use Gremlin or Music2iPod; both are free. Gremlin allows for syncing back to your desktop iTunes library which is pretty awesome too.
Bridge is free though..... I think. There's also a pandora tweak that I can't get too specific about because the mods will get too giddy. But I think you can figure out what it does since we're on the subject of music downloading.
I like to use Mewseek- I don't know why. Its just the first thing I used, so I started making all my downloaders download into that folder (pandora/grooveshark/youtube/safaridownloader..ect)