Bitcoin is the new speculation hotness. Never mind that it costs more in energy to create a bitcoin than the coin is actually worth.
Recently a friend pointed me to some code facilitating arbitrage between bitcoin markets. This sounds interesting, though I imagine it is somewhat difficult to get a really profitable edge- the barrier to entry seems very low. On the other hand, someone else has found a surefire way to profit from the bitcoin speculation bubble: http://boingboing.net/2013/04/18/which-makes-more-money-mining.html
See also: http://bitcoin-analytics.com/
I'll let you know how much money I make from this post!