Slopeys BPC, Thrudds Trading Tool (Not sure if its still around), and I think there is a new one Elite Trading Tool or something like that. While these tools are nice and make trading super easy I would strongly recommend finding your own routes so you don't become reliant on external websites.
In the Galaxy Map under the "View" tab you can tinker with trade routes. Switch off of the Realistic tab on top, then scroll down to the trade data filters (it's right below the faction filters). From there you can toggle on/off all kinds of commodity info. If nothing is popping up try buying the system data for a couple of nearby systems (It's cheap 100cr and can be done right from the Galaxy Map, or you can just fly into the system to get the info for free) this will populate your map with all kinds of cool colorful lines showing which systems ship what to where. It's a great way to quickly see what systems are buying and selling.