I have also made a few other versions to expand the game (not all completely inclusive, but you could modify them to suit your own needs), which are 'finishing positions', 'event numbers' (aka Wilson Index), 'days of the week', and 'all dates of the year'. (See my Google sheets chart at the bottom of this page).
The parkrun alphabet is similar to parkrun bingo, so I have added my progress in another tab (I've never actively worked on collecting specific letters, but as I've toured around I have naturally ticked off most of them without trying).
If you use Google's Chrome browser, there is now a plug-in extension which you can download. It plays with the data on your results page and automatically calculates which challenges you have completed (more than I've listed on this page). A completed challenge results in a badge being awarded - these are all shown at the top of the screen just underneath your athlete details. The green badges show running achievements including the original 'Stopwatch Bingo' plus 'Bushy pilgrimage', 'Pirates!' (7 Cs and an R) and 'Stayin' Alive' (3 Bs and 3 Gs) plus plenty of others. There are also flags which show the countries where you have registered a parkrun - see photo below...
|1st jan 2019|
It also pulls out your volunteering data and gives you purple badges for each role you have performed along with stars which indicate a certain number of occasions in that role (One star for 5, two for 10, three for 25+). It's really simple and brilliant. The extension is made by Team TC Makers and officially called 'Running Challenges', so search the Google Chrome store for 'parkrun' or 'Running Challenges' and it should find the extension.
If you'd like to view the challenges on a mobile phone, you can use the Firefox browser and install the add-on via the add-ons page.
Other useful webpages and tools
Event number predictor (google sheets) - Enter the event number you wish to attend and it'll bring up a list of venues that are approaching that number.
Challenge Chaser - An interactive map for looking up information related to the different challenges.
5k parkrunner results (app - known as the 5k app) - This is becoming the go-to parkrun challenge tracker. It is available for Apple and Android devices. Has some extra features such as a map of venues which also displays those with upcoming cancellations. Also includes your digital barcode, stats, venue information and venue reviews can also be added.