Aigues-Mortes - Salt Town
Aigues-Mortes is a very very touristic little town on the edge of Camargue, actually between Marseilles and Montpellier.
I was a bit disappointed as there is a lot of hype around Aigues-Mortes. It is not as pittoresque as a lot of towns in southern France can be. Eventhough it is a medieval town, most of it is rebuilt in 18th and 19th century, so this is what you get. However, it is very close to Montpellier (20-30 min by car), Nimes and Arles, and the natural reserve of Camargue starts here. For the beaches, check out Saintes-Maries-de-la-Mer in Camargue and its nude beach about 15 east of the town center on the dunes.
You won't find Ibiza/Cannes style here, but you do have some good bars and clubs in town, and if you are looking for alternative activities, you even have a few gay places in town - though most of gay activities are to be found in Montpellier. Look for the rainbow flags in Aigues-Mortes - there are some in the main drag (pun not intended;)
As Aigues-Mortes is not really a beach resort, and if you are looking for more mainstream beach life, you will find a lot of it in neighbouring La Grande Motte (15/20 min by car and public transport respectively), which is horrifyingly modern resort - beware of police who do mind if you wander about without T-shirt in town - you will get fined about 200 EUR. More pleasant little resort is 3 km from Aigues-Mortes, Le Grau du Roi, which has served as the harbour for Aigues-Mortes.
Beaches are otherwise nice - you might find the Mistral wind problematic, because it does get sand in your eyes on the beach.
It might be interesting to taste the local wines of the Camargue area, they are quite reputed. Also check out the wines and vineyards around 30 km west of Montpellier, you will find some nice surprises in eg. Gignac, Aniane, St Saturnin etc... villages in L'Herault. It is around 1 hr drive from Aigues-Mortes but worth it.