Crowdsourcing is looking to the public for ideas or solutions. It usually saves the company money, because either they don't pay the "crowd" at all or they only pay the author of the best idea. It also helps the company profit, because the "crowd" knows what consumers need, so consumers are actually going to buy/use the product.
Examples of Crowdsourcing
The Netflix Prize was an open competition to improve the Netflix's predictive rating system by 10%. The winner won US$1,000,000. The competition was open to anyone who was not connected to Netflix and was not a resident of Cuba, Iran, Syria, North Korea, Myanmar, or Sudan. In August 2009, Netflix announced it would run a second competition.
reCAPTCHA is a system developed at Carnegie Mellon University that uses CAPTCHA to help digitize books while protecting websites from bots attempting to spam them. On September 16, 2009, reCAPTCHA was aquired by Google. reCAPTCHA is currently used for digitizing the archives of the New York Times. The system is reported to solve 200 million captchas every day and it is used by such popular sites as Facebook, TicketMaster, Twitter and StumbleUpon.
Wikipedia is often cited as a successful example of Crowdsourcing, but many people, inclucing Wikipedia's co-founder Jimmy Wales, disagree with that statement.