Despite its scale and emplacement in the capital, it was not in fact the country's first. It boasts a total of around 20,000 bikes and 1,800 stations which are not only spread throughout Paris proper (approximately every 300m) but also into the suburbs which make it much more of a commuting option than the London's Barclays scheme. Its name, Vélib', is a combination of the French words for bicycle, vélo and liberty, liberté; the same principle has been used for the city's new car sharing scheme, Autolib'.
Thanks to its scope and ease of use, Vélib' is hugely popular with tourists and given the distances in the city between many of the attractions, there is no need (unless you wish) to go over the 30 minutes journey time given for free when you hire a bike. Whether you decide to take a one-day (1.70 euros) or seven-day (8 euros) subscription, you'll pay the same charges for every half an hour used after the initial 30 minutes: 1 euro for the first half hour, 2 euros for the second and 4 euros for the third and subsequent chunks of 30 mins. Seeing as you can pretty much cross the entire breadth of Paris in just over 30 minutes (if you pedal hard) you could very well use the bikes to get anywhere you need throughout your stay.
For more info, visit the Vélib' website.London, Barclays Hire Scheme New York, Citi Bike