The definition of "stable" for Debian means that the version number of every piece of software is frozen. Only security fixes (through security uploads) and critical fixes (through point releases) can get into the distribution if they are backported to work with the version currently in Debian. You don't get the latest software but you are ensured that an upgrade won't break anything.
Since the freeze is around 6 months, this means you get 6 months old software when Debian is released. There are some exceptions, like browsers that are too difficult to maintain at the same version.
We believe most people like this definition. This can be frustrating when you need the latest version of nginx but you are happy that upgrading some basic stuff won't break anything on your system: no deprecated configuration option in X, no command-line flag that doesn't exist anymore in Y. All should work exactly as before, with fewer security holes and bugs at each upgrade.
However, if you really want to have the latest version of a selected set of software, have a look at the official Debian backports. This is a great strength of Debian over Ubuntu (where backports are almost inexistant with the notable exception of the kernels): there are many backported packages. For example, if you need a more recent version of nginx and you are running Debian Wheezy, you'll get nginx 1.2.1. If you need something more recent (because you want to get SPDY), you can get nginx 1.6.2 through backports. See here: https://tracker.debian.org/pkg/nginx.
Backports are packaged from the versions that will be in the next Debian release. So, they should keep the same quality than the packages which are currently in Debian. This is a great strength over random PPA. Some of them are maintained by skillful people, some others are not. If you trust Debian for its packages, the backports are made by Debian Developers too.
For nginx, there is no 1.8 because backports are taken from the next release. As this next release is currently frozen, the version proposed in backports is still 1.6.2.
Using a Debian Stable with backports should allow you to get what you want: stability for most packages but latest releases (and latest bugs/changes) for a selection of packages.
Since the freeze is around 6 months, this means you get 6 months old software when Debian is released. There are some exceptions, like browsers that are too difficult to maintain at the same version.
We believe most people like this definition. This can be frustrating when you need the latest version of nginx but you are happy that upgrading some basic stuff won't break anything on your system: no deprecated configuration option in X, no command-line flag that doesn't exist anymore in Y. All should work exactly as before, with fewer security holes and bugs at each upgrade.
However, if you really want to have the latest version of a selected set of software, have a look at the official Debian backports. This is a great strength of Debian over Ubuntu (where backports are almost inexistant with the notable exception of the kernels): there are many backported packages. For example, if you need a more recent version of nginx and you are running Debian Wheezy, you'll get nginx 1.2.1. If you need something more recent (because you want to get SPDY), you can get nginx 1.6.2 through backports. See here: https://tracker.debian.org/pkg/nginx.
Backports are packaged from the versions that will be in the next Debian release. So, they should keep the same quality than the packages which are currently in Debian. This is a great strength over random PPA. Some of them are maintained by skillful people, some others are not. If you trust Debian for its packages, the backports are made by Debian Developers too.
For nginx, there is no 1.8 because backports are taken from the next release. As this next release is currently frozen, the version proposed in backports is still 1.6.2.
Using a Debian Stable with backports should allow you to get what you want: stability for most packages but latest releases (and latest bugs/changes) for a selection of packages.