Side-by-side contact form and GMap using panels
I found a way:  


I enabled "GMap Macro Builder" which comes with the GMap module.  
Added a text format by enabling filter "GMap Macro expander" at the page "admin/config/content/formats/add" and named the text format as "Gmap Macro".  
Created a map macro at the page "map/macro" to paste into a node.
Created a node at "node/add/page" by pasting the macro text copied from the step 3 into the node body, chose a text format "Gmap Macro" which was created from the step 2 and gave a title 'Location'.  
Created a panel page with two columns layout and url "contact-us". Added the contact form to the left column.  
Added the existing node "Location" created from the step 4 into the right column.  
Created a main menu link with the path "contact-us" which is the panel page url.


Finally, I got a contact form with a google map side-by-side.

Required modules:
1. Chaos Tool Suite ( Chaos tools and Page Manager enabled )
2. Panels ( Panels only enabled )
3. GMap ( GMap and GMap Macro Builder enabled )