Plenty options. My favorite is TuneSync[1] which syncs your iTunes playlists over Cable or Wifi. There's also DoubleTwist (an iTunes clone) and about a dozen other options, some of which let you mount the phone as a filesystem, some specialize in syncing playlists with various apps.
The nice thing about TuneSync is that it can be configured to automatically attempt a sync whenever Wifi is enabled, or at regular intervals. That means in practice it will just sync whenever it comes near the computer. I sometimes quickly adjust my playlists in iTunes before leaving the house - and they sync while I'm already half out the door.
I'm longing for an intelligent way to sync. I have just now 200 GB of mp3s (and I'm not alone, nor exceptional, and I still have several hundreds CDs to convert), so syncing 1:1 simply can't work at all until we have terabytes in our portable devices.
I’m luckily still under 64GB (about 39GB, I sync 256kb/s AAC files because I can’t hear the difference) and it looks like my storage needs will grow slower than available SSD storage.
At least I think that’s the case. My music library grew by about 8GB in the last year but 2010 has been an exception. It’s usually around 3GB since about 2000 (I was twelve back then). If my music library continues to grow by 8GB I have until 2013 to get something larger than 64GB. That should be doable.