May 272013
insert into data_you_thought_was_gone
  select how_it_looked_before,
  from   data_you_thought_was_gone
           as of timestamp 
           sysdate - interval '1' hour
  select how_it_looked_before 
           as how_it_looks_now,
  from   data_you_thought_was_gone;

Flashback to the rescue again! This approach will only work if you're notified of the data deletion 
before your undo retention runs out, otherwise you've got to go your backups. You may need to add 
further filtering if there's been updates to your data as well as deletions too. Still can come in very 
handy in certain scenarios though :)

For a script to see this in action, click here. For a thorough explanation of flashback, have a look at this oracle-base article.

Jan 092013
create restore point 
guarantee flashback database;
Be wary; guaranteed restore points consume space in your flash recovery area until (explicitly) dropped,
which can lead to embarrassing space errors if you forget they're there!

For a worked example of this in action, have a look at this article in Morgan’s library.