For some reason it's left out of 12.04LTS so needs to be added in
manually if you need it. Not too onerous and full instructions are
here:

www.liberiangeek.net/.../add-enable-screensavers-in-ubuntu-12-04-prec\
ise-pangolin/

Lots of screen savers but a couple are listed though not actually
installed so not usable.

BTW - have the final release running on a spare PC and getting to
grips with it. Does help a lot getting rid of the global menu but
Firefox still needs it disabling in its add-ons before it accepts the
change.

www.liberiangeek.net/.../disable-the-global-menu-in-ubuntu-12-04-prec\
ise-pangolin/