What is the easiest way to add a Visual Studio 2008 Context Menu Item?

Imports System
Imports EnvDTE
Imports EnvDTE80
Imports EnvDTE90
Imports System.Diagnostics

Public Module ContextMenu

Public Sub DoSomething()
    'Few declarations'
    Dim SolutionExplorer As UIHierarchy
    Dim Item As UIHierarchyItem
    Dim SelectedItem As EnvDTE.ProjectItem

    'Getting the solution explorer'
    SolutionExplorer = DTE.Windows.Item(Constants.vsext_wk_SProjectWindow).Object()

    'Iterating through all selected items'
    For Each Item In SolutionExplorer.SelectedItems
        'Getting the item'
        SelectedItem = CType(Item.Object, EnvDTE.ProjectItem)

        'Do some stuff here'
        If SelectedItem.FileNames(1).EndsWith("txt") Then
            MsgBox("We got the text file!", , SelectedItem.FileNames(1))
        Else
            MsgBox("We got something else...", , SelectedItem.FileNames(1))
        End If
    Next
End Sub
End Module