Convert Photoshop animation to spritesheet

I have an animation that I have exported to gif, works perfect and all, but it is for a game and therefore I need to create a spritesheet for display. Also, I may be creating other animations for the spritesheet, the current animation is a character running maybe adding jumping, etc.

First off, is there an easy way to export an animation to a spritesheet? Secondly, what about adding other animations, I can do the cut and paste manually but is there an easier way?