This worked for me after trying all the other suggestions here:
1. Connect your Iphone to iTunes
2.Select Your iphone in the iTunes Devices list (Side bar/Column down the left-hand side which also has "Library" and "Store")
3. In the main area of the window, click on the "Summary" tab.
4. Tick/Check the box "Manually Manage Music and Videos"
5.Go back to your iPhone icon in the "Devices" list mentioned in step 2. Click on the triangle next to the iPhone icon.
6.Select 'Music' from the drop-down menu now revealed
7. (Courtesy of Macworld!)
The nearly-hidden Autofill feature in iTunes 8.1
At the bottom of the main sync area, you’ll now see the Autofill pop-up menu, which lets you designate the source from which Autofill should choose its music. Click on the Settings button to choose the other options: whether or not to replace all items each time you auto-fill, to choose items randomly, and to choose higher-rated items more often. You can also set aside a particular amount of space on your iPod for disk use. Click on Autofill to fill up your player.
Note; The more music you want to fit on, the less you want to reserve as "disk space' in the Settings above.
This is the only was I have found so far of just getting my music onto my phone. It's probably not ideal in the long run (one would like to be able to select artists, albums, playlists as per normal obviously), but at least it doesn't leave you musicless for the time being!
hope this was of some use. :-)