Vast HTML

This plugin keeps people from viewing your site if they are using Internet Explorer 6. Gives options to download a variety of newer browsers.
For more information on the plugin visit: http://vasthtml.com/js/wordpress-block-ie6-plugin/

Block IE6

This Wordpress plugin will block IE6 users with a choice to upgrade.

Gecka

Display a configurable warning for Internet Explorer upgrade.
Choose to display the warning for versions before IE8 or before IE7.
Choose to always display the warning, or once per session, or once a day, or every 30 days or every year.
The plugin configuration appears in the Reading Settings page.
(based on <a href="http://code.google.com/p/ie6-upgrade-warning/" rel="nofollow ugc">ie6-upgrade-warning</a>)

Gecka IE Warning

Display a configurable warning for some versions of Internet Explorer

Block IE6 vs Gecka IE Warning