iHandler is a free Adobe Air app that can export music from iTunes in Mp3 format. We have covered one tool before called iExporter that can export complete playlists from iTunes. But iHandler works the other way around, instead of exporting the complete playlist you can export selected songs only.
After you have launched the program, it will automatically detect your iTunes music library and list all songs. You can choose the custom path where you would like to save the mp3 songs, by default it is set to desktop. You can select multiple songs by pressing Ctrl and then selecting as many songs as you want. Once done, hit Export Selected Songs button to begin exporting them to the selected directory.
It is a dead-simple tool that actually works. It is still in early stage and the User Interface needs some further polishing.
It works on all Operating System where Adobe Air is installed. Enjoy!