December 2

This one comes to you compliments of www.extendoffice.com

The following short VBA code also can help you display all of the hidden sheets at the same time.

1. Hold down the Alt + F11 keys in Excel, and it opens the Microsoft Visual Basic for Applications window.

2. Click Insert > Module, and paste the following macro in the Module Window.

Sub UnhideAllSheets()
Dim ws As Worksheet
For Each ws In ActiveWorkbook.Worksheets
ws.Visible = xlSheetVisible
Next ws
End Sub

3. Press the F5 key to run this macro. And the hidden sheets will be displayed at once.

From: http://www.extendoffice.com/documents/excel/524-excel-unhide-worksheets.html