The Woolong (symbol: ₩) is the standard unit of currency in the Cowboy Bebop universe. Woolongs are rarely traded in physical form such as in banknotes and coins; it seems that the 2071's economy is based on digital cash.
It appears to be greatly devalued by today's standards. For example, in Mushroom Samba, a single watermelon costs one thousand Woolongs, while in Stray Dog Strut, the Pet Shop worker said that Ein could probably sell for only 2 Woolongs, although given that this is less than a dollar us, this figure is likely an exaggeration by the shopkeeper.
In session 15, "My Funny Valentine", we see a list of Whitney's debts, including 30 million Woolongs for a house, and about 7 thousand Woolongs for 'Donino' pizza. With some of these valuations, and assuming Domino's pizza prices haven't changed within the last 60 years, one dollar US most likely equals somewhere around 100 Woolongs. While this figure fits best, it still leaves us with some inconsistencies in the valuations; for instance, Whitney's bounty would be about $19 (1,900 Woolongs) which would lead us to believe a woolong is worth more, while the price of pizza is up to $70 (7,000 Woolongs) which would lead us to believe a woolong is worth less. Either way, this allows us to estimate that a 2 mil bounty is worth somewhere around 20,000 dollars
The Woolong has been adopted as a currency by bitcoin-based Twitter tipping service, BTCTip. One Woolong is equivalent to one millibit or 0.001 Bitcoin, which is worth $0.01 at January 4 2013 exchange rates.
The Woolong has additionally resurfaced as the currency used in Space Dandy, which features many of the staff from Cowboy Bebop.