In Views, how to allow users to toggle between a grid and list?
If you want to do something like this,


then you can use QuickTabs Module

So, here user can switch from TAB-ONE to TAB-TWO .. so on .. 

To implement this, first you have to create View-Blocks and then you have to create Quick Tabs by using QuickTabs Module

Here is one Video Tutorial to create QuickTabs.