The invention provides, inter alia, novel bisphosphonate compounds and methods of making and using. In embodiments, the invention provides compounds and methods in connection with research and therapeutic applications, e.g., for tumor cell growth inhibition, activation of gammadelta T cells, inhibition of farnesyldiphosphate (FPPS) and/or undecaprenyldiphosphate synthase enzymes, bone resorption diseases, cancer, immune disorders, immunotherapy, and infectious diseases. In regards to certain embodiments, a surprising advance has been the recognition that certain structural features can significantly enhance the activity of the compounds. For example, the presence of particular cationic species e.g., phosphonium, sulfonium, and arsonium moieties can contribute to desirable functional activity when positioned near a bisphosphonate moiety. In other embodiments of non-nitrogen containing bisphosphonates, terphenyl and benzyl bisphosphonate compounds and methods are provided. Further variations are also provided.