While I personally don’t have the time or energy to involve myself in online games (or most other kinds), and really have no interest whatsoever in the stock market, Blog$hares seems like the kind of thing that could prove highly entertaining. To quote from their instructions:
“BlogShares is a fantasy stock market where weblogs are the companies. Players invest fictional dollars on shares in blogs. Blogs are valued by their incoming links and add value to other blogs by linking to them. Prices can go up or down based on trading and the underlying value of the blog. No actual ownership of blogs is transferred. BlogShares is purely a fictional marketplace.”It is free to play at the basic level, or you can pay to become a premium member.
This blog’s page is here (or you can click on the Blogshares icon on the right). I’ve “claimed” the blog and have voted on the “industries” it belongs to. Once you register, you too can vote on blog “industries” (moderators have to check your votes before they count, to avoid spurious attribution of industries) and acquire shares of your favorite blogs. You'll get a good sense of how it works by looking at the page for this blog and others (probably more than by looking at the game's home page, which seems geared toward people already playing). So, if you’re into that kind of thing, go forth and trade.