Northern Rail have introduced a new Day Rover Ticket- the Northern Explorer- for £35 for 1 day/£60 2 days/£90 3 days/£110 4 days, no railcard discounts.
There are also group versions for 2,3 or 4 adults, and 50% off for children.
It covers one day travel anywhere on the Northern network (bounded by Newcastle, Carlisle, Windermere, Chester, Buxton, Stoke on Trent, Whitby, Lincoln, Nottingham and Crewe)
There are no time restrictions on use, and can be issued on demand at stations and all Northern ticket machines.
As long as you stay on Northern trains (so avoid faster trains on Avanti, LNER, TPE, Cross Country etc) it is quite a good deal.
There are many cases where it will be cheaper than a point to point single- eg Manchester Airport to St Bees for the coast to coast walk, if no walk up Advance Fares are available. It is certainly easier than doing complicated split ticketing.