You need to enable suspending as one of the options under the General tab in `System->Preferences->Power Management', and click `Enable Suspend'. Once you've done this, the option will appear in the logout dialog.
** Changed in: gnome-session (Ubuntu) Status: Unconfirmed => Rejected -- No sleep option on logout https://launchpad.net/bugs/55399 -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs