Just install the Music WithMe app on your smartphone and the desktop software on your computer. Select the playlists you want to download and Music WithMe will automatically read your iTunes account.
WithMe app works over a WiFi or standard data connection and promises a seamless listening experience to your iTunes library. WithMe downloads playlists from iTunes directly your smartphone. Once playlists are downloaded you will not need a data connection to listen. This should save your battery some juice.
The app is available on the Android Market right now for $14.99 and you can get a free 30-day trial. I think $14.99 is a bit much? Try it free for 30 days and see what you think.
Check out their site @ http://music.withme.com/