The history of scientific discovery is littered with examples of "pathological science" - an area of research where experimenters are tricked into accepting false results by a combination of subjective effects, unrecognized experimental errors, and wishful thinking. The term was first used by Nobel-winning chemist Irving Langmuir in 1953. Langmuir described pathological science as an area of research that simply refuses to die long after it was given up on as false by the majority of scientists in the field. He called pathological science "the science of things that aren't so".
Enter Cold Fusion. From the initial spectacular announcement by Martin Fleischmann and Stanley Pons (at a press conference, no less), to its equally spectacular flameout under the weight of irreproducible results, the lack of a theoretical framework, and scathing accusations of "incompetence and delusion" on the part of Fleischmann and Pons, cold fusion appears to have been consigned to the scientific landfill along with perpetual motion, polywater, and the canals on Mars.
Or perhaps not. Although mainstream science has long since turned its attentions elsewhere, Cold Fusion, these days known as Low-Energy Nuclear Reactions (LENR), has been kept alive by a small but dedicated band of mostly fringe researchers, publishing in their own set of publications.
It's still infuriatingly difficult to reproduce experimental results, but 25 years of work have started to bear fruit. LENR effects have been observed in numerous experiments using a variety of methods, and theoretical explanations are beginning to take shape.
Based on current thinking, LENR - and not cold fusion - may in fact be the correct name for the phenomenon; the Widom-Larsen theory posits that the observed results aren't due to fusion at all, but low-energy nuclear reactions that involve neutron formation from electrons and protons/deuterons, followed by local neutron beta-decay processes. That theory explains a number of problems with the original explanation, including the Coulomb Barrier, the lack of observed radiation, and so on. Needless to say, that theory itself is widely disputed by the traditional physics community.
Next: Adding fuel to the fire