Some time ago I wrote a post regarding this same topic (installing an updated version of Nginx instead of the one that is on the official Ubuntu repositories) but for Hardy (8.04).
Now, it is the turn of the latest Long-Term-Support version of this Linux distribution.
In this case, we need to use this repository:
deb http://ppa.launchpad.net/nginx/stable/ubuntu lucid main
You can create a file like /etc/apt/sources.list.d/nginx-stable.list, and put that line inside.
We also need to add the key of this repository so Ubuntu won’t complain.
apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 00A6F0A3C300EE8C
and finally, run:
apt-get upgrade && apt-get install nginx