Depends what your interests are. Berwick on the Borders has a number of bridges over the river Tweed & almost intact town walls, Lindisfarne Castle & Priory are worth a visit, tides permitting (access via causeway). Budle Bay is a good place to observe waders. Craster & Dunstanburgh are well worth a visit. Park in Craster, walk along the shore to Dunstanburgh Castle. The beach just north of Dunstanburgh Castle gives a good view of the cliff the castle sits on. Warkworth & its Castle are worth a look too. If you head out of Warkworth heading towards Amble you can get a good view of the castle looking back. South of Bamburgh, Seahouses is a small village, its harbour is popular with divers (not sure how popular this time of year). It used to be a fishing harbour years ago.
Inland, there are some attractive places to explore, Wooler, Ingram Valley (near Powburn) is very scenic. Alnwick & Alnwick Castle (was used in some Harry Potter films).
