Anguilla, St. Barths and Saba are the closest neighboring islands to St. Martin/St. Maarten, close enough for day-trips. Whether you fancy a deserted beach in Anguilla, a jungle trek through the mountains of Saba, a taste of the 'Good Life' in St. Barths or the peace of 'off the beaten track' paradise in St. Eustatius, journey times are negligible.
Slightly further afield are the islands of St Kitts and Nevis, Barbuda, Antigua and Tortola, and if you are on an extended vacation to the Caribbean, pretty much every island is accessible, with well timetabled flights and innumerable boats and ferries for your chosen 'island-hop'.
Anguilla: Regular ferry service, primarily from Marigot, but also from Philipsburg and from a dock next to the Princess Juliana Airport. Regular air service from Princess Juliana Airport.
St. Barths: Regular ferry service from Philipsburg, Oyster Pond and from Marigot. Regular air service from both airports.
Saba: Regular ferry service with the Edge, leaving from Pelican. Regular air service from Princess Juliana Airport.