They've got muck; we've got rakes. TPM Muckraker
Intrade runs a "market" for current events - traders buy and sell contracts based on what they think might happen. As more traders buy into an event happening, those events become more expensive; the market spikes for that event, and its likelihood is predicted.
As James Suroweicki elegantly explained in his book, "The Wisdom of Crowds," any one expert is fallible, but the sum of many opinions, even those of non-experts, is often surprisingly accurate. In 2004, Intrade says, its 2,000 participants accurately predicted the presidential vote in every state, as well as the outcome of 33 of 34 Senate elections.