Fritzing comes by default with a pretty large library of parts that you can use in your designs, and new parts are being added to that library all the time by various contributors. However, there are also a few large part libraries outside of that, that you might want to add to your installation. The biggest ones are probably the libraries of parts made by the companies that sell those parts:

• Adafruit
• Sparkfun
• Seeedstudio

See the README in the Adafruit's library for detailed instructions on adding those to your Fritzing.