Bussard, who also invented stuff like the Bussard ramjet and nuke rockets, recently made a few talks briefing his research under the Navy's embargo, detailing his Polywell fusion theory, and passed away not long afterwards.
To make a long story short, the theory is very promising (much cheaper, simpler and more efficient than e.g. the Tokamak), but hasn't really caught on with any funding to match its promises, yet.
It seems to be getting more attention, though, which can only be a good thing if (as it seems so far) it can deliver everything it's supposed to.. E.G make fossil fuels nearly obsolete, relatively overnight.
http://cosmiclog.msnbc.msn.com/archive/2008/01/09/566532.aspx