Paris public transport has always been stellar, with an tight network of subway (métro) stations, commuter rail (RER/SNCF), and buses that can can get you within spitting distance of anywhere in the city, quickly and economically. But the implementation of the Velib bike-sharing program two years ago put Paris public transport a whole other level, by any measure--ecological, economic, public health, noise pollution, etc.
There are over 10,000 Velibs parked at over 1000 parking spots across the city. For a euro or day, or 5 euros a week, or 29 euros a year, you get an unlimited number of rentals lasting 30 minutes. Thirty minutes is enough to get you from Drupalcon to almost anywhere downtown. Need 45 minutes to bike somewhere? No problem, just find a Velib parking lot (they are rarely more than 200m away), park the bike you're riding, and pick up a new one. You could daisy chain your rides all day if you wanted to...
