Do you want to test drive any theme or perform some backend actions on your active wordpress installation?

Here are few plugins that can help:

Maintenance Mode

Adds a splash page to your blog that lets visitors know your blog is down for maintenance. Logged in administrators get full access to the blog including the front-end.

Visitors will see a message like “Maintenance Mode – SITE is currently undergoing scheduled maintenance. Please try back in 60 minutes. Sorry for the inconvenience.”

http://wordpress.org/extend/plugins/maintenance-mode/

Theme Test Drive

Theme Test Drive Wordpress plugin allows you to safely test drive any theme on your blog as administrator, while visitors still use the default one.

It happens completely transparent and they will not even notice you run a different theme for yourself.

Best part is you can even set the testing theme options (if it has them) in the Admin panel while you are testing the theme.

http://wordpress.org/extend/plugins/theme-test-drive/

and

http://wordpress.org/extend/plugins/theme-preview/

PLEASE PROMOTE THIS POST