I enjoyed the Keep on the Borderlands and the Slavers series from 1st edition.
Aren't some of the newer 4e modules supposed to be "adventure sites", less railroading and just more adventure hook type stuff?
The 4e modules or adventure paths, are very much on the rails. I tried to run the Scales of War from the Dragon magazine and it ended (pardon the pun) in a total train wreck. Everyone felt like they were being forced to do something that they were not interested in. Also, no one could keep track of the convoluted schemes going on around them (I tried to add some intrigue on the side). My group only plays for 4 hours every two weeks, and we all have short memories. We have opted for more of a sandbox approach. I just let the players decide what they want to do. Nothing is pre-planned to start with. Though later I can build encounters later, in response to what they have chosen to do. Random encounters got thrown back into the mix. Regardless what WotC says, not all encounters need to be meaningful to the plot.
I found this blog post (Less plot, More Story)a few weeks back, and I couldn't agree more with what he has to say. Especially since I had already started doing this before I read his post.