This clip shows you how to buy items in FarmVille without spending your precious coins. In another word, no coins will be subtracted from your balance. It's a pretty cool hack, you will have unlimited coins.
You'll need to download the Freezer Bot, you can download from farmvillecoinfreezer.blogspot.com.
Even though it is a hassle because it requires you to complete a survey, but it's probably safer than downloading from another site because those may contain malware/spyware.
This will be posted on the forum page too, so feel free to contribute your experience, questions, or try to help others out that have troubles with this hack. Have fun.