Here is a link from Mac OS X Hints that might help:
macosxhints.com - 10.4: Backup, restore, resize, and convert Boot Camp partitions
-Keith
Update: After I read the comments section for the link above I am not very confident in the information. However, I left the post there in case you want to check it out on your own.
Update 2: If your bootcamp partition is NTFS, it looks like this would be a good choice:
Winclone