A way to search for journals that are in a similar area to a given journal
The Scimago Journal Rank does this reasonably well for journals in specialized fields (example). However, if you look at a given journal (example) there can be many subject areas listed, so unfortunately it isn't a great tool for finding similar journals that cover multiple areas.


Just don't rely too much on such lists. They're good for exploring what's out there, but the various scores it provides should be taken with a grain of salt. And as D.W. wrote in this answer,


  There is no shortcut. If you are knowledgeable about your field, a random webpage is not going to know your field better than you do. If you are not knowledgeable about your field, then the first thing you need to do is to fix that.