Last January at the NASA Innovative Advanced Concepts Symposium, Gary Hudson, head of the Space Studies Institute, outlined the experimental investigation that James Woodward at California State University Fullerton has been doing for many years into the question of whether Mach’s principle leads to propellantless propulsion. (See Gary’s talk in this NIAC 2014 video.)
Recently Charles Platt posted an interesting update on Woodward’s work : Strange thrust: the unproven science that could propel our children into space – Boing Boing.
The Space Studies institute has been providing some funding for Woodward via SSI’s Exotic Propulsion Initiative. There is a donation button there if you would like to help the project.