The ubiquitous iPod, in 20 GB white/silver ($299) or red/black special U2 edition ($349) with battery up to 12 hours and 2" grayscale screen holds roughly 5000 songs with touch-sensitive controls. Compatible with Mac or Windows and plays mp3, AAC, M4A, M4B, Audible 2, 3, 4, WAV and AIFF.