This 1.6-ounce thumb-size MP3 player packs unmatched battery life: 50 hours on a full charge. Even more notable, the quick-charge function gives you three hours of playback after charging for just three minutes. Sony bolstered the lithium-ion battery's life using software that allocates precise amounts of power based on what the player is doing (rather than operating at full power all the time). It supports MP3, WMA, WAV and ATRAC3 formats. $120 (512MB) or $150 (1GB)
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.