The guys behind RailCommute recently sent me a copy of their iPhone app for checking your usual rail route. The app is aimed at people who generally use the same rail route and want to check on train times and platforms plus any service disruption. You store your home and destination stations and can then pull up 'trains to work' or 'trains to home' with a simple tap.
The app lets you tweet or update your Facebook status with the train you're on although not sure when I'd want to do this!
You can also view the Twitter feed for your local train operator to check for problems.
At £2.99 the app is aimed at people who don't need the full functionality of something like the £4.99 UK Train Times app. It uses the same National Rail data feed so everything should be spot on. For price and simplicity this app gets my vote.