Sorry: This Week in Steam is no longer active.
Between 2012 and 2019 this page showed a summary of when steam-hauled trains were expected to pass through selected UK mainline stations, using data from UK steam info. People would use this information to run down to the trackside and wave as the trains steamed past.
The This Week In Steam page was populated by a well-behaved web-scraper that visited UK steam info in the wee hours every night, figured out when and where all the trains were going, and then reorganised that by station, linking directly to the relevant tour page on UK Steam Info.
UK Steam Info was a splendid site run by the late David Randles (a respected authority on sonar and a volunteer signalman on the West Somerset Railway), who did a sterling job collating and publishing the original data that made this possible (most users, and indeed web developers, underestimate the crucial and thankless work that goes into making data both available and useful). When Dr Randles fell ill in 2019, the UK Steam Info site lost its driver, and so this remote project, the Beholder web-scraper, was retired.
OpenTrainTimes does have beautiful UK mainline source data, but there seems to be no way to identify which trains are steam-hauled... so This Week In Steam has been shunted into a siding and decommissioned.
Maybe the RailAdvent [sic] site is the best place to find out when steam might be passing your way (in the UK). They do provide a “railtours through Railway Station” tool, but you have to pay for it, and it's a single-station query-box interface, so it's not quite as helpful as This Week In Steam used to be.
For those times when you need to get somewhere so badly you’re even willing to be hauled by diesel or electricity, Matthew Somerville’s traintimes.org.uk is the most accessible way to get to the online UK train timetables. Unlike the official service, this has hackable, bookmarkable URLs, ultralightweight page load (so it’s urgently fast when you use it standing on the platform), and service worker optimisations for full-on nerdy usefulness.