Diborane can be produced in situ by reduction BF with NaBH (see for Flavopiridol). Usually however, borane dimethylsulfide complex BHS(CH) (BMS) is used as a source of BH. It can be obtained in highly concentrated forms. 
The adduct BH(THF) is also commercially available as THF solutions wherein it exists as the 1:1 adduct.  It degrades with time. 
Borane adducts with phosphines and amines are also available, but are not widely used. Borane makes a strong adduct with triethylamine; using this adduct requires harsher conditions in hydroboration. This can be advantageous for cases such as hydroborating trienes to avoid polymerization. More sterically hindered tertiary and silyl amines can deliver borane to alkenes at room temperature.