The following works fine, but I am thinking this modifies the $httpProvider globally, which isn't what I want.
angular.module('SessionService', ['ngResource'])
    .config(function($httpProvider){
        $httpProvider.defaults.headers.post['Content-Type'] = 'application/x-www-form-urlencoded; charset=UTF-8'
    })
    .factory('Login', function($resource){
        var resource = $resource('/adminui/login',{},{
            post:{
                method:"POST",
                isArray:false
            },
        });
        return resource;
    })
LoginCtrl = function($scope,Login) {
    $scope.login = function(){
        Login.post($.param({user:$scope.user.username,password:$scope.user.password}),$.noop,$.noop)
    }
}
Is there anyway to do this instead?
...
    .factory('Login', function($resource){
        var resource = $resource('/adminui/login',{},{
            post:{
                method:"POST",
                isArray:false,
                headers:{'Content-Type':'application/x-www-form-urlencoded; charset=UTF-8'} // ignored
            },
        });
        return resource;
    })
The "headers" parameter seems to be ignored. the request is still
Content-Type:application/json;charset=UTF-8 
Is my value for headers ok?