Need Subscribe Wordpress Plugin Like Mashable

[glaxxon]

Hey everyone,

I have been looking for the subscription plugin for my blog. This plugin can be seen on the right side of mashable.com
http://mashable.com/2011/05/09/connect-with-mashable/

I know a free plugin exists as i have seen the exact same thing in many other blogs too, but i can't seem to find it.
Can someone please tell me where to get it.

Thanks