I've noticed that some members of my team were having difficulties with Visual Studio when using resource files. Any time they would open a file it would crash Visual Studio. As you can imagine this was very frustrating for all involved.
After a quick search I found a pretty neat alterative editor called 'Simple Resx Editor' by Matías. Currently this resource editor is at version 0.6.2 but it is being worked on at the time to improve the functions available.
The main benefit I like about this editor is that you can open all your resource files, side by side and edit them all in one quick go. This is a perfect setup when dealing with multiple languages as it really speeds things up. If you just want to work on one resource file and you need to know what the Key Name values are simply click on the big Key icon on the top of the app. This little app is small, quick to use and really offers a benefit over the built in editor in Visual Studio in my opinion.
The only snag I noticed while working with the editor is that if you had a very long Value field there are no scrollbars showing. I've left a message to Matías about this issue and I'm sure this will be fixed in the next version of this software.