Is there an easy way to diversify your Bitcoin holding among the other popular forks? Recently there has been a spread of Bitcoin clones, starting with Namecoin and following with other newer clones. There is a chance these coins will appreciate relative to Bitcoin.

Is there an easy way for a Bitcoin holder to automatically diversify his holding among the different crypto currencies, similar to holding an index fund or ETF instead of purchasing individual stocks?
Sidestepping the comments about whether or not Namecoin is a fork or a separate project or whether bitcoin is an investment or a currency, I'll address the direct question asked: Is there a way to easily and automatically purchase several crypto-currencies at once? Not at present time, no.

Bitcoin (and its forks) is a very young project, though, and I'm sure there was a stock exchange before DJIA or S&amp;P existed. Give us time and it's very likely that something of the sort will be created - especially now that the demand has been made publicly known.