You can still use Limewire.... If I am correct, you should be able to sync your music to the Verizon program, and it will search for the music that you have on your computer, regardless of where it is. Once it locates music, it will allow you to copy it to the program....
You can pretty much use any program, and the program will scan the music, as long as the music is saved in a file on the computer. Me, I prefer ARES.
I no longer use the program, becuase many phones hold a memory card, and its easier to drap and drop the music directly.