Ile de Re - for cycling, beaches, walks, wildlife, meal out - I would recommend St Martin de Re for meal and people watching, Ars en Re for markets, pottering and Bois en Re for beaches.
La Rochelle - Aquarium is a great day out, good shopping, visit old port and nice and compact to walk around.
Royan - La Palymre zoo - lovely spread out zoo and great for kids (though polar bears are a bit sad)
Saintes - for history/Roman ruins etc..
Cognac - nice history, shady cafes and walks - and urm...cognac :)
Puy du Fou - a bit of a drive (hour and a half) but worth it - honestly (see previous threads for tips etc...)
Les Sables d'olonne for alternative beach life, zoo, shopping, shell museum etc...
Ile d'Oleron - less commercial than Ile de Re but nice walks, fishing villages and beaches
Rochefort for history and jazz festivals in July/August (Wednesdays)
Hope this helps