Try this. Click anywhere in your range of data and then use this macro:
Sub CombineColumns()
Dim rng As Range
Dim iCol As Integer
Dim lastCell As Integer
Set rng = ActiveCell.CurrentRegion
lastCell = rng.Columns(1).Rows.Count + 1
For iCol = 2 To rng.Columns.Count
Range(Cells(1, iCol), Cells(rng.Columns(iCol).Rows.Count, iCol)).Cut
ActiveSheet.Paste Destination:=Cells(lastCell, 1)
lastCell = lastCell + rng.Columns(iCol).Rows.Count
Next iCol
End Sub