One easy, but far from perfect, method is using different a PREFIX, this will work for most (but not all) ports.
For example:
Code:
# cd /usr/ports/shells/zsh && make install clean 'PREFIX=/usr/pkg/${PORTNAME}-${PORTVERSION}'
I used /usr/pkg to keep things seperate from "normal" ports in /usr/local...
Instead of FORCE_PKG_REGISTER you can also use a different PKGDB, but changing PKGDB never worked very well for me, but in this case the plist isn't that interesting anyway because you can jst remove /usr/pkg/zsh-1.0 to remove everything....
You will also need to add the binaries to PATH or use symlinks.