Extracting Text from PowerPoint format
Here are different ppt extraction code. No guarantees, please modify list information if you test it.
Using Apache Tika: http://tika.apache.org/
Here is some sample code that works with some ppt formats. It's basically an implementation of a POIFSReaderListener. There are no guarantees on how well it works - it is known to ignore unicode text records for starters. It requires POI libraries.