I was sure that I would find this question, but I couldn't. How to create an isolated development environment? It other words, a sandbox, where I can install different combinations of web servers, databases, other software packages and play with them, without cluttering my system packages and without manually downloading packages from official websites. Something for software stacks as virtualenv + pip is for Python.
Before that I tried to install OSes inside QEMU/KVM, but that is an overkill and a bit complicated (couldn't set up bridging, for example). Is it possible to create isolated virtual environments without running virtual machines with full-blown operating systems?
I use Debian GNU/Linux.
Edit (01.08.12): A similar question on Unix.SE with more elaborated answers - http://unix.stackexchange.com/q/31136/11397