I personally prefer
http://www.eddb.ioUnlike some that seems to be catering to those with a spreadsheet fetish, it's very concise, big bold print.
Particularily the loop feature, and that it can remember your ship settings (granted it requires making a login)
What site you would choose doesn't really matter, since most use the same database, what differs are presentation and some of the backend maths in the queries but there's no real secrets here, so most sites present the same routes.
The really great profit runs aren't necessarily shared with these sites since that way everyone would do it.
But I have seen routes ran by dozens of players each carrying 400t-500t each, and the prices has yet to change over the past few months.
The over all on average commodity with the most profit are imperial slaves, this means traveling to the empire and thusly almost anyone winds up in the empire because of it.
Now there are plenty almost as good commodites to trade, but since imperial slaves are so routinely better the databases presents them more often, seeing trade's in federal space for instance would almost require black listing imperial slaves.
If you don't want to use tools trading do not click on any of the following links.
Here's one I have been using a little, on off for the past month or so.
http://eddb.io/trade/loop/8229There is really just a few hundred credits differing between trading in slaves and not.
I remember doing this particular run in mid july, and it's still good.
http://eddb.io/trade/loop/12883Both of these can be a single jump with a
d grade type 6, b grade FSD netting you a little over a quarter mil every two stops, trade for an hour and you have earned back the t6.