Of the Paizo adventure paths, I liked Rise of the Runelords and think Kingmaker has some really really good sandbox elements, although the actual kingdom-building didn't, in the end, do much for me.
I'd say try to find a bunch of old Dungeon magazines. I love using their 3e modules. They often had very good ideas. Wotc's free adventures that were available for download were often also quite good, although they needed some work a lot of the time.
For a longer plotline with some real creativity (although the "middle third" can get a bit draggy) try to find the Night Below boxed set.