Symmetrize Weights adds the ability to make the weights of a vertex group symmetrical in Blender. It is part of a series of scripts I've written as I've started to learn and use Blender for my personal projects. Symmetrize Weights is released under GPL v3.0 and is intended for Blender 2.63.
Symmetrize Weights is in the Tool Shelf in Weight Paint mode.
To Install Symmetrize Weights follow the normal procedure with installing addons.
For those unfamiliar with this process, open the Blender User Preferences (Ctrl + Alt + U). Go to the Addons tab. Click the Install Addon button, browse to where you downloaded the addon and select the python file. Make sure that the "Testing" category is selected under Supported Level. Type the name of the addon into the search box, and click on the enable addon checkbox.
I'm currently using Blender to create a small short film. I'm still learning Blender, and it's largely a linear process as I learn what I need to accomplish for each stage in my personal production. There are large gaping holes in my current knowledge of how to use Blender. Because of this, the scripts I'm releasing now are all in the "Testing" stage. It is very likely that they will have bugs related to my lack of current knowledge. Even worse, these scripts could be implementing a feature that already exists!
I don't know how far my little project will go. I don't know if or when I will be able to use Blender in my professional career. Therefore, I have no way of knowing if the scripts I write now will ever reach a more polished state. Given the open nature of Blender, my hopes for the future of Blender itself, and my belief in the copy-left movement, I've chosen to release these scripts in their current unpolished state.
I sincerely hope that they are as useful to you as they have been for me. If you're a script writer who is interested in these scripts, please don't hesitate to fork them!