A perfect excursion from Javea is to the Port/Resort of Denia just 11km away over the mountainous CV736 road. So, why visit Denia?
Denia has the feel of a very thriving Spanish Port with daily boats to Ibiza (on a clear day you can see the island from the castle, 100 km away), a busy shopping zone, pavement cafes and a Moorish castle.
Shopping is generally located in the centre on the Calle de Marques de Campo and there are some cool boutiques for non-UK fashion styles if that's your thing. Market day is worth a look and is held on Fridays. Be prepared to park a bit further out on this day because the town becomes very full. As you head up this main street you will come to a roundabout with a fountain and there are some nice chiringuitos here.
Denia celebrates more Fiestas than any other town in Spain, which is some achievement. The biggest is the Hogueras de San Juan (June 22-24) which is similar to the Fallas in Valencia - papier mache figures are paradedthrough the streets and then on the 24th set fire to. In July there is the running of the bulls into the sea, and in August a Moors & Christians fiesta.
The Castle has a small museum telling the town's history. Like all this area, it was held by the Moors till the 15th century and was the taifa (local region) capital which explains the castle. If I remember rightly you can drive right up to the castle.
The ferry to Ibiza takes about two hours and costs between 90€ and 270€ depending on whether you go on the high speed boat (perhaps unfairly nicknamed the vomit comet) or the conventional ferry. Here's a link to make a ferry booking between Denia and Ibiza.
If there's anything you think I should add about Denia, let me know