Even though Pokemon GO isn't even one month old, there already are plenty of tools and apps related to the game. As far as Pokemon maps are concerned, there are several options available, but so far, the only one that I believe is actually helpful is Pokevision. This recently launched online service gets its information directly from Ninantic servers, accurately identifying the Pokemons that spawn in your general area and showing you exactly where they're located.
Pokevision is an online tool that you can access from any device with an Internet connection. All you have to do is to use the search bar from the top-right corner of the browser to enter the city you're in and the tool will automatically show you a map of the area. Then, navigate until you find your current location and tap or click to place the marker where you are. Lastly, press the big red button at the bottom of the map to scan around you for Pokemons and the application will identify them, showing you where they are. Additionally, you can use the filtering button (the one from the upper-right corner, which states how many Pokemons are currently being shown) to filter the scan and look for specific Pokemons. What's really cool is that the tool also displays the amount of time left until the Pokemon disappears from that spot so that you know when you need to hurry or if you won't get there in time to catch it.