Every Wednesday during the summer, Es Cana hosts a now famous hippy market. Here you will find hundreds of stalls, some selling genuine local artifacts and ornaments, others selling more tacky t-shirts and tourist trinkets.
But whatever is your "thing", it is a very pleasant morning wandering around the myriad of stalls on offer, watching local craftsman making ornaments. It can get very busy during the peak summer and it feels like tourists descend from all over the island to the market (most resorts run buses on a Wednesday to Es Cana ).
There are very few markets like this on the island (if any), so have a visit if you are staying in Ibiza.