>In using Oracle's SQL*PLUS, is there any way to have the last several commands typed to reappear or does one have to always retype things?
>SQL>

You can copy and paste in the sql window.
For selects the 'l' key lists the previous select and you can change any part of it with the 'c' key. For instance the list might return...

1. select * from db
2. where field1 > 10 ;

you can then type l2 (list line 2)
and change c/10/5/ to change 10 to 100

type '/' to rerun the sql
'l' list would return

1. select * from db
2. where field1 > 5 ;