Export data tables from SQLPlus
SQL*Developer is a decent tool for this, but can still take some time. 

If you're looking at SQL Plus, I'd recommend that you use spool, and make liberal use of SQL Plus's set command to format your output into flat files. For delimiting the flat files, you can make use of the concatenate feature to add in column headers. Here's an example:

select 'col1,col2,col3,col4'
  from dual
union
select col1||','||col2||','||col3||','||col4
  from some_table;


HTH.