Ever seen animated textures in
SL? Those are done with a texture tiled with the various animation "frames" and a script that sets the texture offsets quickly. One of these images looks something like this:
The idea of making one of these textures by hand was horrific, so I made a little tool to generate them. Woot, woot!
GIF 2 SL Animated Texture
The LSL script for playing the animations is on the page too. The program names the created image so that it can just be uploaded and thrown into a prim with the script.
Note: Unfortunately it only works on Windows machines for now, and you need the .NET 2.0 Framework. This software is distributed with no guarantees, it doesn't work for all GIF images and sometimes crashes with a cascade of application exceptions!
However, it works most of the time

Enjoy!