Here a link to the map:
http://avidblur.com/arma2/
In the small towns there's probably a couple building with anything worthwhile. Some of the big cities have 5-6 building with great loot but you're more likely to run into bandits. There is also 3-5 military bases/airfields that have great weapons but again you'll run into a lot of resistance.
It all depends on how you want to play. For the first week or two I played more as a someone who focused on surviving so I avoided people, got loot by sneaking around, and was almost always in the woods avoiding towns. Now I'm thinking of doing a quick run to get automatic weapons and then just become a bandit and rob fools. Just generally fuck around because you will die and lose all your stuff.