Bicing is a new component of the public transportation system in Barcelona. The system consists in a series of over 100 stations all over the city, each one with approximately 15-20 bicycles that you can borrow automatically using a card. To obtain this "bicing card", you must register through the Web and pay an anual fee of 24 euros ($33 USD).
The system is very simple. By approaching the card to the station's base, one of the bicycles is freed and the screen shows the number of that bicycle. Then the user can use the bicycle for 1/2 hour and return it to any of the stations. Each extra hour costs 0.30 euro ($0.40 USD). This extra is paid through the credit card that you must use to obtain your bicing card.
In practice,
bicing is excellent. It is more comfortable than having a bicycle as you don't have to worry about leaving chained in the street or having to take you bicycle upstairs to your flat or office, and there are always many bicycles available. It is very good as a complement to metro or bus, or to move faster through the city than by foot.
The WWW is an important part of the system, as all the process for registering and obtaining the bicing card is done via web, and you can also block the card and request a duplicate if you loose it. The credit card that you must use when registering is an effective way of making people take care of the bicycles and keep them in good conditions.