It's always interesting to see people convering bicycles to electric-drive, and the following example by PJ Allen is a well-explained and quite successful conversion. With a simple bike from a garage sale, he's added an electric scooter motor and has created a PWM-control circuit based around an Arduino and some FETs. The electronics side of the project is relatively simple compared to the physical work involved in mounting the motor and drive system, however it would be a fun project. In the following video you can see the creator taking some test-rides:
For a detailed description of the conversion process and some other interesting reading, visit the project website. And for more, we're on twitter and Google+, so follow us for news and product updates as well.
If you're making a similar project and need to control large currents with your Arduino digital outputs - you'll need a MOSFET. We've got you covered with out NDRIVE: N-MOSFET driver/output module:
This high-power N-MOSFET module lets you switch high-current loads using a tiny microcontroller. Perfect for controlling that set of traffic lights mounted in your living room, electric motors via PWM and other automotive projects such as switching high-power 12V lights and high wattage LEDs. For more information and to order, visit the product page.