Friday 17th May - Arts & Culture Festival - 1 night only for free.....
Light Nights - a free night out in Liverpool (Nottingham seems to run a similar event but in February and I'm not sure if that is an annual thing or not sorry folks!).
lightnightliverpool.co.uk/ - for further details
I went last year and have a lovely time, Merseytravel reduce their rates on the night too.