You must stop using it at all until you can see what to recover...
Data Rescue...
http://www.prosofteng.com/products/data_rescue.php
Virtual Lab...
http://www.binarybiz.com/vlab/mac.php?PHPSESSID=48b398a7879fa364a82736a2b9bf955a
You need another HD with plenty of space to recover to.
You should use another Boot Disk or other Mac with this one in Target mode to do the recovery.
They have a free demo to see what it could recover.
rccharles on file recovery...
"Stellar Phoenix Macintosh - Mac data recovery software, recovers data from damaged, deleted, or corrupted volumes and even from initialized disks."
They have a trial version, so I guess you can see if your data can be recovered...
http://www.stellarinfo.com/mac-data-recovery.htm
FileSalvage is an extremely powerful Macintosh application for exploring and recovering deleted files from a drive or volume. FileSalvage is designed to restore files that have:
* been accidentally deleted.
* become unreadable due to media faults.
* been stored on a drive before it was re-initialized/formatted.
http://subrosasoft.com/OSXSoftware/index.php?main_page=product_info&products_id=1