What is the most efficient way to draw voxels (cubes) in opengl?

I would like to draw voxels by using opengl but it doesn't seem like it is supported. I made a cube drawing function that had 24 vertices (4 vertices per face) but it drops the frame rate when you draw 2500 cubes. I was hoping there was a better way. Ideally I would just like to send a position, edge size, and color to the graphics card. I'm not sure if I can do this by using GLSL to compile instructions as part of the fragment shader or vertex shader.

I searched google and found out about point sprites and billboard sprites (same thing?). Could those be used as an alternative to drawing a cube quicker? If I use 6, one for each face, it seems like that would be sending much less information to the graphics card and hopefully gain me a better frame rate.

Another thought is maybe I can draw multiple cubes using one drawelements call?

Maybe there is a better method altogether that I don't know about? Any help is appreciated.