[freebeard]

Not saying that's the best example. Quoth Wikipedia:

Principles of operation and design
The electric sail consists of a number of thin, long and conducting tethers which are kept in a high positive potential by an onboard electron gun.[2] The positively charged tethers deflect solar wind protons, thus extracting momentum from them. Simultaneously they attract electrons from the solar wind plasma, producing an electron current. The electron gun compensates for the arriving electric current.
[snip]
The electric solar wind sail has little in common with the traditional solar sail. The E-sail gets its momentum from the solar wind ions, whilst a photonic sail is propelled by photons. Thus, the available pressure is only about 1% of photon pressure; however, this may be compensated by the simplicity of scale-up. In the E-sail, the part of the sail is played by straightened conducting tethers (made of wires) which are placed radially around the host ship. The wires are electrically charged and thus an electric field is created around the wires. The electric field of the wires extends a few dozen metres into the surrounding solar wind plasma. The penetration distance depends on the solar wind plasma density and it scales as the plasma Debye length. Because the solar wind electrons affect the electric field (similarly to the photons on a traditional solar sail), the effective electric radius of the tethers is based on the electric field that is generated around the tether rather than the actual tether itself. This fact also makes it possible to manoeuvre by regulating the tethers' electric charge.