I did a quick comparison of bitcoin stock exchanges today and thought I'd share my initial impressions.  Please let me know if I missed any major exchanges, or if I got the wrong impression anywhere:

MPEX
website: primitive
30 day volume: 22,000 btc
listing fee: 30 btc!!!
other comments: They operator seems insufferably rude.  You can see it in his FAQ.  These guys are best known for handling the recent SatoshiDice deal.  Between the high fee and rude operator, it's not clear to me why people use this service.

BTCT
website: so-so
30 day volume: 108,000 btc
listing fee: 5 btc
other comments: Based in Bolivia.  You can really sense the legal uncertainty of bitcoin securities on this websites.  There are huge, very verbose disclaimers all over the place.

Cryptostocks
website: nice!
30 day volume: 300 btc
listing fee: 2btc!
other comments: looks great.  I'm not sure how long they've been around.  Maybe they're new and that's why the volume is so low.  I dig the low listing fee.

BitFunder
website: nice!
30 day volume: not sure, but I think it's very high
listing fee: 5btc
other comments: another great-looking site.  Everything seems professional

That's it.

The reason I'm looking into this is that I'm thinking of doing crowdfunding for a literary project, and rather than appealing to straight philanthropy, I thought it'd be more fun and effective to sell shares of the proposed book.  Is anyone aware of this having been done before?  I'm not.  Any thoughts are appreciated.