If you’re into both virtual stock markets and Twitter, this should be right up your 140-character alley. Meet Pretweeting, a fairly new website that lets you spend and earn virtual cash by buying and selling words on Twitter.

Here’s how it works: you sign up through Twitter (using OAuth) and get $5,000 virtual USD to spend on bundles of shares (or 10,000 ‘slots’) for words that you think will soon become hot on Twitter.

The most likely to become widely used are the most expensive words to buy (e.g. ‘the’ will cost you $44.9 per share, ‘you’ $25.57 and so on) so before you get sucked in you might want to compare the value of words on Twitter before purchasing using this widget. There’s a leaderboard on the site that identifies the most prolific ‘pretweeters’ and you can tap into the NYTimes’ TimesWire if you’re having trouble finding words that could propel you to the top of that list.

A couple things you need to know about the game: there is a 5% fee for each sale, the minimum purchase price for any word is $0.05 and only tweets in the United States are counted.

I enjoyed playing around with the virtual stock game a lot, but I don’t like the fact that the box for auto-tweeting was hardly visible and ticked off by default, resulting in a couple of unwanted tweets inserted in my Twitter stream.

Other than that, good fun ($1.45).

(Hat tip to eHub)