This is a very small (just one aspx, no code behind, ~130 rows) file that will show you everything you have in your cache. It can be very handy sometimes to see exactly what you have in the cache and even try and remove some things and see what happends.
The GUI is very easy, it just lists everything and the type/value and if it is serializable you will even be able to see the serialized value of the cache item.
Please note that you need to change the RemoveFromCache method if you want to use it with EPiServer CMS 4.
You can download the source here (Right click and save target as)