Search for "porterbox" on the Developer Machines page.
Porterboxes are generally configured to allow regular users to create new chroots using schroot. The DSA team has a short tutorial about how to use schroot on porterbox machines. By default, all DDs should have access to porterboxes, but you can request guest account accesses if necessary.
Short version is:
schroot -c sid
This will build a new chroot using the sid template and chroot into it. The environment will be destroyed when you exit.
It is recommended to use screen to switch between chroot and normal environment.