Available for download from the Internet Archive, a remarkable number of 80s and some 90s computer games, courtesy of the TOSEC project (the Old School Emulation Center). These include several Doctor Who games - for instance, download a Spectrum emulator and you can be off playing "The Key to Time", or a decent Commodore 64 emulator and there's "Doctor Who and the Mines of Terror" and "Dalek Attack", write-ups of all of which can be found at the invaluable Millennium Effect website. No BBC Micro games, alas, but it's still rather fun and not a bad way to spend a few hours.