Best way to select & move 3D object in OpenGL with mouse?

Can anyone post simple sample how to select (say, with the mouse left button) some specific object (for simplicity, a sphere) out of two others and move it with mouse from one location (x1,y1,z1) to another defined location (x2,y2,z2) ?

Do you know utilities in OpenGL which (like GET_RGB_VALUE@ in 2D graphics) allow to get the color of the pixel in OpenGL screen?