Downtown Orlando is an option. It's not the most exciting place you have ever been but if you head around Lake Eola it's a nice place to walk, and Thorton Park (just east of Lake Eola) is a nice quaint neighborhood. If that is your type of thing, then head up to Winter Park and walk around there. If you really want a low key thing, they have this small boat ride (uses a pontoon boat) that goes between a couple of lakes along these little canals.

Of course the theme parks are the big thing, but Orlando does have a number of smaller parks. And you didn't say why you didn't like the parks - Downtown Disney Marketplace is an interesting place - you've got a bit of the vacation vibe going there, quite a few people, but no admission, no rides. You can always see Cirque.

Not too much for museums in the area, but they have a small art museum and a science museum. You might also check out Leu gardens.