Alpatronix C3 Ultra-Portable Mini Capsule Speaker with Enhanced Bass & 3.5mm Audio Jack for Apple iPhone, iPad, iPod, Samsung Galaxy, Nexus, HTC, Blackberry, Nokia, Smartphones, MP3/MP4 Players, Tablet, PC, Laptop [SONPRE EDITION] - (Black)
I'm not an audiophile or particularly experienced with speakers (yet), but at $15 I'm quite satisfied with this one. The lead is very short, so your phone's sort of locked down whenever you're plugged in, but the speaker itself is very convenient and projects surprisingly well.