Bitcoin
Bitcoin is an "alternative currency" that is generated electronically with no central authority, with a loosely-connected set of network nodes engaged in "minting" coins by solving difficult mathematical computations, validating such newly-created "coins", and storing transactions involving them. This is all accomplished algorithmically.
A bitcoin, and its associated transactions, can be represented in various ways, even including actual physical metal coins if you can believe the picture in the Wikipedia article. A binary format is defined in the Bitcoin technical specs, but archived Bitcoin blocks in the "Block Explorer" site are displayed in a JSON-based format (served as text/plain).
The smallest possible unit in a Bitcoin transaction is .00000001 bitcoins, also known as a satoshi.
Contents | 
Data format info
Other specs and definitions
Software
Sample files
- Block Explorer: a Bitcoin archive
 - The "Genesis Block"; first Bitcoin block ever generated
 - Genesis block in some other formats including raw binary
 
Current and historical prices
News coverage
- Government Ban On Bitcoin Would Fail Miserably
 - Bitcoin ATM
 - Bitcoin value reaches new high against US dollar (that was $32; as of late 2013 it's now over $600)
 - Hackers steal over $12,000 in bitcoins
 - Bitcoins Seized by DEA
 - Bitcoin's vast ovvervaluation seems to be caused by usually-illegal price fixing
 - Person gets windfall from Bitcoins he forgot he owned; bought for $24 and sold for around $1 million
 - A Bitcoin Exchange Holding $4.1 Million For 1,000 Customers Has Simply Vanished
 - Sir Richard Branson's Out of This World Plan for Bitcoin
 - James Howells searches for hard drive with £4m-worth of bitcoins stored
 - Chinese government says Bitcoin cannot be used as currency
 
Academic papers
- Paper criticizing Bitcoin (and the concept of decentralized currencies)
 - Paper showing that selfish mining behavior could end up dominating Bitcoin
 
Commentary
- My adventure in donating bitcoins to the Internet Archive
 - Open source governance in Bitcoin
 - Anecdote about the wrong way to promote Bitcoins
 - The Bitcoin Network is 0 FLOPS
 - How the Bitcoin protocol actually works