Menu: Tools -> Options -> Environment -> Documents
Now, by popular demand, Visual Studio 2010 comes with the option to put newly opened documents in the File Channel to the RIGHT of existing tabs. This has been a long requested feature and it is finally here!
Just go to Tools -> Options -> Environment -> Documents and select the "Insert documents to the right of existing tabs" option.
You should now see any tabs you open pop up the RIGHT of all the other tabs: