Using Rails for the internal app makes even more sence then for an external app :-)
As the requirements are (usually) more lax you will be able to use something like Streamlined to add the basic CRUD operations and then just add some business logic on top of that.
Eclipse is an IDE and has almost nothing to do with the web technology you use. In fact the popular RadRails IDE is just a set of Eclipse plugins packages together (or something like that)
