Is there a keyboard shortcut to show/open the Trash?
If you are using a Spotlight or a program such as Quicksilver that allows you configure keyboard shortcuts to perform actions. Here is a solution, create an AppleScript run only Application that will open the trash can for you. Its not a built in command but is should fit the bill nicely and you can do it all with built it tools.


Open AppleScript Editor 
Open a new script editor window if one did not already open.
Enter the follow in to the blank editor window

tell application "Finder"
    open trash    
end tell

Test the script, press Run, trash should open.
Save the Script with the name "OpenTrash" make sure to select "File Format:" Application and check the "Run Only" option.
Open the newly saved OpenTrash Application, trash can contents should open in the Finder. 


Introduce it to your favorite program launcher, and set up keyboard shortcuts etc. Also note that spotlight should index it as well and you can use that to open the Trash can now too.

&#8984; + space  and then search for "Tr"... Then press enter  once "OpenTrash" is highlighted.