Regarding #254: I like the colors, but what is the object (logomark)? It looks like a tie.
Regarding #242: This is an interesting abstraction of a shell, but unfortunately it is a nautilus shell (not the kind you can blow through).
Regarding #257 and #255: I like the image of this shell, but it looks like it would be a small shell that would fit in the palm of your hand. Also, I like the typeface, but it would nice to see some contrasting color.
Note that nobody has submitted a logo that depicts noise coming out of the conch. I'd be interested to see if that is possible.