the tdk a33 is supposed to provide good sound quality for ~$90, though it's a somewhat big and heavy-ish bluetooth speaker.
the boom urchin is ok if you want something more portable and ~$60. Doesn't have great sound quality, but is acceptable and comes with some accessories for attaching it to things (suction cup, carabiner, adhesive mount, tripod thread).
note: the above suggestions are based on wanting something weather resistant and battery powered.
A bit more information might be helpful:
are you looking for one that's battery powered? mildly weatherproof? portable?
what kind of music/audio do you plan on listening to?