You can use sqlplus to format the data you want and then spool the data to a file. You can then use sqlldr to load in the data. Try something like this:
SQL> set echo off newpage 0 space 0 pagesize 0 feed off head off trimspool on
SQL> spool mydata.txt
SQL> select column1 || ',' || column2 || ',' || column3
from <tablename>;
SQL> spool off
This works fine for a table or two but I'm not sure how useful it is if you want to do a full export of the tablespace.