I don't know if this has been mentioned on here before, but I only just found this site today.
Basically every month there is a different race for a charity, generally 5k and 10k option. You pay your race fee ( seems to be £10-15 on average) and the money goes to the charity. You run the distance at any point you want during the month, and take a photo of your Garmin display or running app, which you email to them as proof, and they send you your medal or t-shirt or whatever. The results are published online.
Seems a great fun way of raising money for charity and incentivising your runs, and ideal for those who don't fancy the farrago of racing with hundreds of other sweaty runners.