Change the number of home screen panels in Android
If you don't want use 3rd party apps:

This requires decent computer skills and a rooted phone, but here are the steps for android 2.3 Gingerbread.


Copy /system/home.apk from your phone to pc.
Decompile home.apk using apktool.
Goto [decompiled folder]/res/values/integer.xml    
Change &lt;integer name="number_of_desktop_panes"&gt;5&lt;/integer&gt;, to 7 or whatever you want.
Save it,and compile the apk using apktool.   
Copy it back to phone i.e to /system,change its permissions to -rw-r-r.