Does any one know how to do this?
You can use GParted to achieve this, as it supports HFS+, FAT32 & NTFS resizing.
if you want to reduce the size of bootcamp partition you can use this.
and if you want to increase the partition size you can use CampTune.
if you want do it free use this method (Malicious link removed -- see comments) it needs 2 applications (both are free)
p.s: some software download link in article was corrupt you must download these apps from my links.