Dieppe is the nearest beach to Paris, lively all year round. It is well-known for a failed landing operation by predominantly Canadian Allied forces during WW2, on the 19th of August 1942. You won't find a French flag flying in Dieppe without a Canadian flag alongside it. Dieppe has a long and interesting history, having been an important port linking William the Conquerer's kingdom of England with his native Normandy Dukedom in the 11th century, and having endured centuries of conflict right up until 1944. Today, it's an important ferry and fishing port, and a pleasant seaside resort.
The Transmanche Ferry  from Newhaven, England carries cars and foot passengers across the English Channel in about 4 hours for 15 pounds each way. The ferry has a bar, shop, restaurant, and lounge deck. Arrive by train from Rouen (40 minutes - 10 Euros) or Paris (2 hours - 22 Euros). The town also has a small aerodrome, situated in Saint-Aubin (2 miles away).
Dieppe is a small town with a population of about 35,000 (54,000 for the metropolitan area called Dieppe Maritime). Most of the tourist destinations are within walking distance of hotels, but you can hire bicycles for a few Euros per day from opposite the tourist information office in the harbour area.
The Saturday morning market is a must-see. It is one of the largest and one of the most popular markets in Normandy. From 8am to 12:30pm you can find almost everything there.
For French grocery products, try chez Olivier, in the rue Saint-Jacques. A lot of good cheese, wine and coffee can be found there.
There are plenty of traditional French restaurants, especially seafood restaurants, around the quayside area. Most of them are located on the street Henry IV. Comptoir à Huîtres, La Marmite Dieppoise, La Moule Qui Chanti, Le Grand Duquesne, Le Bistrot du Pollet, Le Havre and Les Voiles d'Or are all very good restaurants. QG serves excellent crepes. They can all be found in the town center except for Les Voiles d'Or, situated just opposite the Bonsecours chapel.
You won't find a veggie restaurant in Dieppe—they're rare in France. In fact, vegetarians will have a hard time in most French restaurants. Three good options are the excellent Turkish Ankara restaurant (rue de la Rade, near the harbour entrance), the Taj Mahal Restaurant (Quai du Hâble) and La Bekaa (Quai du Carénage) that serves good vegetarian cuisine.
The café des Tribunaux, situated in the heart of the city, is the oldest and the most popular café in town. It often gets crowded at weekends but has a very nice atmosphere to it. For a town of its size, Dieppe has quite a few bars and pubs, and most of them stay open late (2am weekdays/4am weekends). For good cocktails, try the Epsom and the Europe on the seafront, the Cactus and the Pirate on the Quai Henry IV or the Cambridge pub in the town center. For a very French ambiance, you can try La Potinière, le Douze or le Mieux Ici Qu'en Face, three rather cheap and very popular small cafés. On weekends, you can listen to live bands at the Epsom on the seafront, the Au Bout Là-Bas on the Quai Henri IV and the BDB (rue des Bains). There is also a large nightclub close to the town centre: the Panama Club.
Dieppe is a small and safe town. Simply be aware of your surroundings if you are out late at night in the town centre, where the bars and pubs are located. You'll find the police station next to the town's train station, on the Boulevard Georges Clemenceau.