There is a guy on Wall street, John ‘JP’ Paulson, that made big bets against the housing market by taking the other side of those dodgy mortgage backed securities – the ones that crashed to worthless recently. (Basically he bought default insurance really cheaply)
His relatively small funds were up $15 billion n 2007, and his net worth up from about $100m to $3-4 billion. Not a bad year.
Meanwhile this year seems to be starting off with a thud rather than a bang. Shorting is your friend in these times.