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).

Data format info

 * Protocol specification

Other specs and definitions

 * Blocks
 * Address
 * Transactions

Software

 * Bitcoin software on Sourceforge
 * Bitcoin-Qt client

Sample files

 * Block Explorer: a Bitcoin archive
 * The "Genesis Block"; first Bitcoin block ever generated

Other links and references

 * Wikipedia article
 * My adventure in donating bitcoins to the Internet Archive
 * Government Ban On Bitcoin Would Fail Miserably
 * Bitcoin ATM
 * Bitcoin value reaches new high against US dollar