EDIT: BEFORE YOU ASK ME QUESTIONS REGARDING THIS TUTORIAL OR ANYTHING ELSE TO DO WITH GIFS, LOOK AT THIS PAGE.

I hope this makes sense for everyone who reads it. Let me know if you have any problems. :)

Just so you know: This tutorial was written assuming the person reading already knows how to make standard gifs. :)

In Photoshop (I use CS5), have the two (or however many) animations open in separate documents, making sure each of them has the same amount of frames.

In one of the documents, click “Select All Frames” and then “Copy Frames” in the animation bar menu.

Then go to the second animation. The size needs to be changed to fit the other gif in, so go Image > Canvas Size (or Ctrl + Alt + C).

Make sure to change the anchor. That’s important. I’ve done it so I can have the next animation to the left of that one, but if you want it on the top, just select the bottom center anchor, and change the height instead of the width.

We’re left with:

Now in this document, go to your animation bar menu (refer to the earlier image if needed), and click “Select All Frames”, and then click “Paste Frames…” (it’s underneath Copy Frames)

Make sure you’ve checked “Paste Over Selection”.

And then you’re done! (Well, you can continue editing colours/whatnot like normal after that.) You can also continue adding more than two animations using the same steps.

End result (without any further editing):