USPS and Royal Mail, US and UK, present day.
Federal Reserve, Bank of England, US and UK, present day
BAA, UK, established 1966, monopoly on London airports persists
Railtrack, UK was established in 1994 as a monopoly. British Rail had held monopolies previously
GlaxoSmithKline, held a monopoly on Azidothymidine, a drug for HIV treatment until 2005