Bitcoin

Of course I'd heard of Bitcoin, but Joe B. at work pointed out that there were ASICs coming out that are supposed to crank the mining hash rate.  Butterfly Labs is one of the companies producing specialized machines.  (The FPGAs are more interesting since you could repurpose them later, but they have higher power consumption and lower hash rate.)

Seems pretty risky, though, since a bunch of ASICs will probably be coming online at the same time.  BFL's FAQ has an entry on this that seems to imply that one could break even in about 6 mo, but that calculation may lowball the impact of the additional computational power; then again, the exchange rate has also risen about 60% since that calculation.  In other words, it's a total crapshoot.  Another site has a profitability calculator.

There's also a mining hardware chart on the bitcoin wiki.  Some people build custom mining rigs using multiple graphics cards, but the hash rate doesn't even come close to the theoretical rate of the ASICs.  In that regard, investing in one of those might be more sound.  Or it could be better to have the lower rate now before the ASICs come online....