The simple answer to your question is:
ThisWorkbook.Save
Application.Quit

The bad part about that is that it will try to quit the application
regardless of what else may be open.
The code below takes into account the "Personal.xls" workbook
(which is usually hidden if in use at all) and tests to see if anything
else is opened.
Other than the personal.xls workbook, if another workbook is
opened, this will save and exit this workbook.
If no other workbooks are opened, it will save and Quit Excel.

'Option Explicit
Sub CloseAndExit()
ThisWorkbook.Save
Dim WBCount As Integer
WBCount = Application.Workbooks.Count
If WorkbookIsOpen("Personal.xls") Then _
    WBCount = WBCount - 1
If WBCount > 1 Then
 ' user has some other workbook open
     ThisWorkbook.Close
Else
     Application.Quit
End If
End Sub

Private Function WorkbookIsOpen(wbname) As Boolean
' Function copied from j-walk's site
' Returns TRUE if the workbook is open
Dim x As Workbook
On Error Resume Next
Set x = Workbooks(wbname)
If Err = 0 Then WorkbookIsOpen = True _
    Else WorkbookIsOpen = False
End Function

John

Sub SaveAndClose()
  Activeworkbook.Close Savechanges:=True
End Sub

This assumes the workbook is not a new unsaved workbook.

Regards,
Tom Ogilvy