How to billboard+constrain on an axis?

Hi all,

I know that billboard has a normal always face toward the camera, but as normal billboarding doesn’t quite work for oblong shapes, how do I also constrain it to an axis.

Here’s the effect I’m trying to replicate. Note the elongated shape of the “plasma bolts” and the muzzle flash. Both rectangles whose faces are oriented towards the camera.

http://www.majhost.com/gallery/sastrei/BrickSpace2/ss00125.jpg

-Stefan-