With ReSharper, finding dependencies between different projects in a solution is easy. To find which code depends on a particular module, simply right-click the project in the Solution explorer and choose Find Code Dependent on Module from the menu:
This will show you a tree containing projects, individual files, and lines within those files that reference the module.
To find referenced code, choose Find Symbols External to Scope in the same menu. This will locate all the assemblies you are referencing:
As you can see, this also lets you drill down into referenced assemblies code that you are using.