There is so much to do in Deal and the surrounding area:
The salt-marshes, shingle beaches and mud flats of the Sandwich and Pegwell Bay National Nature Reserve offer excellent spotting opportunities. The Sandwich Bay Bird Observatory Trust studies and catalogues the birds, as well as organising classes, talks and guided walks at their site.
There is a cycle path all the way along the sea front to Kingsdown. It's a gorgeous ride in the summer particularly, when the wild fennel is out. Here's some useful information about other routes in the area.
Deal Castle - clamber over the cannons and scan the horizon for enemy ships.
Walmer Castle - official residence of the Lord Warden of the Cinque Ports, with lovely gardens, as well as beautifully preserved interiors.
Dover Castle - check out the bucket of guts in the kitchens! Brilliantly evocative wartime tunnels too.
South Foreland Lighthouse - the first to use electric light, built by the Victorians to guide sailors into Dover harbour.
Sandwich - hop on the train to avoid the £7 toll for cars; Sandwich has some excellent places to eat and a delightful sense of history.
The Romney, Hythe & Dimchurch Railway is such fun: a miniature steam train taking you across the Romney marshes from Rye to the surreal Dungeness nuclear power station (visit nerdydaytrips for other fascinating spots in the area, if you want to make a day of it).
More vintage transport excitement is to be found at the East Kent Railway, in Dover and the Elham Valley Railway Museum in Folkestone (worth ringing in advance to check this is open when you want to visit).