You cannot access iTunes on a third party device. However, you will be able to play the music in a third party player.
MP3 player compatibility with iTunes for Windows
iTunes for Mac OS X: Compatible Players
If your MP3 player does not support MPEG-4 AAC files then you can convert it. For information about converting iTunes files to different formats, http://support.apple.com/kb/HT1550
You can use free software called DoubleTwist for Mac and Windows. It works with almost all usb mp3 players. It can also sync everything in iTunes and in your music folders.
Even though it is reccomended for andriod devices, it still works with usb devices.