Biking in Paris is not for the faint of heart.  But it's not just for the happy few, either.  The city is becoming increasingly bikable, and with the availability of the Vélib' (bicycles you can rent by the day in most quarters of the city), bikes are a definite possibility for transportation.

Cycling in the City

Have your own bike?  Then you can hit the road.  However, keep in mind that motorists are not entirely used to cyclists in the heart of Paris, and you are advised to keep to marked bicycle routes.  (The city maintains an interactive map of these routes here.)  One of the greatest hazards, though, is other cyclists -- don't be surprised to find people riding on sidewalks, up one-way streets (in the wrong direction), or through parks.  It's going to take a few years for cycling to settle down in Paris, but it's headed in the right direction.

Above all, wear a helmet!  More and more Parisians are donning protective gear, so you'll no longer stand out.

Vélib'

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The vélib' is a city-wide system of rental bicycles.  You can pick up a bike and drop it off at any of scores of automated stations throughout the city.  Short-terms users can  subscribe to Vélib’ for a 1-day or a 7-day Vélib’ pass -- available for purchase on the web or at any Vélib’ Service Points.  For online subscriptions, go to the Vélib web site.