I would find it useful if the building names in the /Town/Resources tab gave some indication as to whether one had sufficient resources to upgrade that building.
It can be frustrating to select several different buildings in turn, only to find that one has insufficient resources to build any of them.
Another useful feature would be for there to be an indication on the /Town/Inventory page as to when each resource would fill the storage available, at the current rate of production.
The final thing I have thought of is that it would be useful to be able to create bookmarks of notable places on the World Map - so the ability to store a list of useful places with a short description of why the place is interesting (which would be easier to use than my current method of noting these down in a Google Doc).