If you are a developer then you are in luck. Carnegie Mellon University has released the powerful Sphinx Speech Recognition software as an open source project. You can use the engine in a commercial or research project for free. Since it is released under the BSD license, you donít have to release your source code if you distribute a product (unless you want to).
The C language based Sphinx 3.5 package is the speech recognition engine that was used in the open source Robosapien Dance Machine program, which was SourceForgeís Project Of The Month for May 2005. This version of the engine is speaker independent, which means that you do not have to train the system on a userís voice before they can use it.
We recommend it highly.
Sphinx 3.5 speech recognition engine on SourceForge.
Another free piece of software that is Robodance, a free software package for WowWee, i-SOBOT, Ultimate Wall-E, and other consumer/toy robot owners; including the U-Command Wall-E robot. It is not a general speech recognition package so you canít use the speech recognition for your own projects. But it does give you full voice control over the robots listed above.