Until recently, I thought that FLOSS (Free / Libre and Open Source Software) for harmless partitioning didn't exist. The guys at nixCraft proved me wrong by publishing an article about repartitioning using only open source software (to be more precise, Knoppix and its "qtparted" utility). It's not perfect as far as the English grammar and writing are concerned, but it's fully understandable.
Well, I stand corrected :).
Read the article: How do I resize windows Partition with Open Source Software