Laganas-Zante, you can go and see a shipwreck and the island has the most wonderful beach which turtles live on (therefore water sports are restricted) I am going this Summer and can't wait!
I've been to Skala in Kefalonia and Skala Kalloni in Lesbos. Both fantastic places, more villagey than party central, but with lovely beaches and fab food. I've also been to Kos which was good - but much more touristy that the others.