Here are two solutions for you, depending on the application:
- World aligned materials as suggested by @ClockworkOcean above;
- You can use [Object Scale] node in the material editor. It will give you the scale of any object the material is applied to, and you can multiply your UV coordinated by it. There are some drawbacks, since UV is two-dimensional and objects are three-dimensional, so your material will need to take into account the faces orientation. But you can do that automatically by getting [VertexNormal] and comparing it to world axes. It may seem a bit tedious, but it does the job. It looks something like this:
