Whilst the CONNECT BY functionality has always been nifty, its been a major chore to actually obtain the full hierarchy for a particular node in a hierarchy, often requiring either some PL/SQL or a temporary result set to do it.
9i has a new function SYS_CONNECT_BY_PATH, which is probably best explained with the example from the documentation
SELECT LPAD(' ', 2*level-1)||SYS_CONNECT_BY_PATH(last_name, '/') "Path"
FROM employees
START WITH last_name = 'Kochhar'
CONNECT BY PRIOR employee_id = manager_id;
Path
---------------------------------------------------------------
/Kochhar
/Kochhar/Greenberg
/Kochhar/Greenberg/Faviet
/Kochhar/Greenberg/Chen
/Kochhar/Greenberg/Sciarra
/Kochhar/Greenberg/Urman
/Kochhar/Greenberg/Popp
/Kochhar/Whalen
/Kochhar/Marvis
/Kochhar/Baer
/Kochhar/Higgens
/Kochhar/Higgens/Gietz