There is a very handy utility on the SourceForge web site called the iTunes Agent which enables you to synchronise your iTunes music library with virtually any MP3 player – the only prerequisites are that it support the M4A format used by iTunes, and that when connected to your PC it be listed as a drive within My Computer.
The software is only available for the Windows platform currently.

Download the software from http://ita.sourceforge.net

Once installed, the software will be added to the Programs folder on the Start Menu. Launching it will add an icon to the system tray:

Connect your MP3 player, or mobile phone. If you are connecting the device to your PC for the first time you should install any accompanying drivers before connecting the device.
In the case of the Nokia E-series, install the PC Suite software before connecting the phone via USB.

When connecting the phone, you will be prompted on the handset to specify whether you wish to connect the phone in ‘PC Suite’ or ‘Data Transfer’ modes, select Data Transfer.

Now open My Computer, you should see the device listed as a USB storage device. I recommend creating a new folder on your device called ‘iTunes’ or something similar.

Right click on the system tray icon for the iTunes Agent and select Preferences:

The following window will be displayed:

An example configuration will already be listed, to configure your device do the following:

In the Music Folder section, click on the Choose button. The folder structure of the PC will be listed, browse to the iTunes folder on your device that you created earlier and click OK.

In the Recognise by folder/file section, click on the Create button. Again the folder structure of the PC will be listed, browse to the same iTunes folder on the device and click OK.

In the Associate with playlist section, choose the Playlist you wish to synchronise with the device. If you want to synchronise the entire Library, just select Music.

Click Save to save the profile changes, then click Close.

Now right click on the system tray icon and click Synchronise. The selected music will now be copied to your device:

Once complete, the selected music files will be located in the iTunes folder you created earlier.