A form of financing either through exchanging pre-mined crypto currency other than Bitcoin to Botcoin either directl or through "proxy tokens" (doublecheck).
Usually run to raise start up funds to develop technology infrastructure. Projects like Ethereum had a disclaimer on their page that a crowd sale shouldn't be considered investment.
During Maidsafe crowdsale the initial sale, safecoins were be made available via purchase of a 'proxy token' called MaidSafeCoin. These were recorded on the bitcoin block chain and available from buysafecoins.com at a price of 17,000 for 1 BTC, or 3,400 for 1 MSC (from Mastercoin).