Nice article on the starshade technique to find Earth sized planets.

His telescope, called the "Many Worlds" mission, would launch a telescope nearly identical to the Hubble telescope into an obit around the sun a few million miles from Earth in a region of gravitation stability already used by a few other astrophysical probes. The second part of the telescope would be the "occulted," a 30-meter-wide petal-shaped sail sent to the same region of space but separate from the telescope by a distance of more than 10,000 miles.

Using lasers, the two parts would line up, with the star shade just blocking out the light from a nearby star from the center of the telescope's view. Calculated mathematically to throw away the light from the star but keep the light from any planets it held (this is the "occulting" part of the occulted), the device would be able to detect planets smaller than Earth orbiting stars within 35 light years of Earth, Cash and his colleagues calculate. The key is the petal shape of the shade, which scatters starlight from the telescope's view.

The plan still wouldn't be cheap, perhaps $2 billion, money that NASA doesn't have. But it would use technology available today, a Hubble-size telescope and expandable ribs to unfurl the shade.