Ok, found another one: the
DLO HomeDock for $99 MSRP, so I'm guessing you can get it for less online. Haven't done an online pricecheck though. This is just a dock though, you'll need your own speakers.
I just saw a few of the M604's from my previous post on Amazon for $110 new so their prices are dropping, and some used ones starting at $99.
Also on Amazon, the
INSTEN folding speakers (basically a dock?) that fits both iPod and Zune and the thing is dirt cheap. One of the reviews said it was better than laptop speakers, but I don't know if it would be good enough to play at the beach.