This is a plugin for XrmToolBox. The code is based on the View Layout Replicator.
Even though you can export records from Dynamics CRM, there is a record count limitation. The upper limit is 100,000 in CRM 2015 Update 1 -> http://www.microsoft.com/en-US/dynamics/crm-customer-center/export-data-to-excel.aspx
This tool can be used to overcome that limitation, as it just pages through RetrieveMultiple till there are no more records to retrieve.
Download the most recent version of XrmToolBox. Click on the "Plugin Store" button in the menu and install this tool from the store.
Tanguy for View Layout Replicator - Most of the UI and event handling code is from this tool.