Miro is an open-sourced, free solution to your media problems with Android. It's touted as an all-in-one solution, and with its feature list, I'm not about to disagree. It offers a media player, BitTorrent client, video encoder, music store and device sync component all wrapped up in a single program, which covers some of the problems Android has run into without its own downloadable client.
With your phone connected to your computer, you can use Miro to sync music and video to your phone. It maintains a library by scanning folders, and can even import your current iTunes library on first load.