One town that I love is Moonwood Mill, it is a small world but has no loading screen, other than going into the different lots. This world came in the Werewolf Game Pack. There are not many lots, but the community lots have been combined, for example, there is a gym behind the library. One thing I love to do is to have my sim interact with the world, meaning they can walk, jog around, or ride their bike.
With Expansion Packs, my top favorite is Cottage Living, love the town as well, and the wildlife and farm animals that came with it.
With Stuff Packs, my top favorite is Tiny Living.