In SQL*Plus you can also use the simple TIMING option:
SQL> SET TIMING ON
SQL> SELECT bla FROM bla...
...
Elapsed: 00:00:00:01
SQL> SELECT bar FROM foo...
...
Elapsed: 00:00:23:41
SQL> SET TIMING OFF
This will report timing information for each statement individually.
Another option is to set up individual timers:
SQL> TIMING START mytimer
SQL> ... run all my scripts ...
SQL> TIMING STOP
timinig for: mytimer
Elapsed: 00:00:08.32