The ferry back to Saint-François on Grande-Terre takes 45 minutes and puts you at the eastern end of Grande-Terre, with the whole of Guadeloupe accessible from there. Saint-François itself is a pleasant small town with a marina, a market, and good restaurants.
Pointe-à-Pitre is about 60km west of Saint-François along Grande-Terre — the main city, the ferry hub for the outer islands, and the place to stock up on anything the island doesn't provide. The Mémorial ACTe museum, devoted to the history of slavery in the Caribbean, is here and worth the journey.
Marie-Galante is reachable by ferry from Saint-François in about 45 minutes. Another quiet island, flatter than La Désirade, with old sugar mills, empty beaches, and a reputation for producing the strongest rum in the Caribbean. It makes a good second island if La Désirade has you wanting more of the same.
Les Saintes (Îles des Saintes) — the most photographed bay in the Caribbean, a dramatic volcanic harbour with a well-preserved fort above it. More visited than La Désirade or Marie-Galante, but the setting is genuinely spectacular. Ferries run from Trois-Rivières on Basse-Terre and from Pointe-à-Pitre.