You find currently nginx version 0.7.67-3 in Debian Squeeze. If you want the latest version you have to build your own paket or you can use one from the ubuntu ppa.
This installs the latest stable relase of nginx webserver (current 1.0.1) on Debian Squeeze.
echo "deb http://ppa.launchpad.net/nginx/stable/ubuntu lucid main" > /etc/apt/sources.list.d/nginx-stable-lucid.list apt-key adv --keyserver keyserver.ubuntu.com --recv-keys C300EE8C aptitude update aptitude install nginx
But if you need some third party modules, you have to build your own packages.