While wandering the internet (yet again) I stumbled across these series of articles/bog entries about using Oracle with multivalue data:

Sabarinathan Arthanari has written a series of articles, which hopefully will continue, regarding the use of multivalues within Oracle. They are based at codeproject.com.

And a bit more regarding the collect function within Oracle 10g – http://www.oracle-developer.net/display.php?id=306

All interesting stuff.