There are so many places to go, really. it's all a matter of what sorta things you want to see, cultural, touristy, shopping, nature etc I'm going back for a holiday too this year going to have a better look. Alas it's late so I'm not awake wnough to write a list of the many things you could see.

The one piece of advice I will tell you now, is that in Osaka you want to go to Den Den Town, its like the Osaka equivalent of Akihabara when it comes to collectibles, but generally speaking Den Den town has cheaper prices, and more discounted items.