Cloudflare, a web cryptography company, handle about 10% of internet traffic and have to generate billions of random numbers a day to use as seed numbers for their cryptographic algorithms.
They do this by having a wall of 100 lava lamps, with a camera taking a photo of them every millisecond. These are then translated into image files and further translated into massive strings of numbers by analysing every pixel in the image and assigning it a colour identifier, becoming a true random number generator.
This is because, counter intuitively, electronic computers are extremely bad at generating random numbers. So bad, that it is virtually impossible for any electronic device to generate a truly random number without a physical device connected to it to generate the randomness.