Al-Islam.org has a downloadable PDF called "Diseases of the Soul". It lists vices that harm the soul and that Muslims should avoid. I'm not going to link it, but if you want to read it, just visit the library section at al-islam.org.
The irony of this list being at an Islamic website:
All of these things are fairly self-explanatory, except "backbiting" (also known as "talebearing"). It means gossip or slander. But in Islam, it also includes saying anything negative about the religion, whether it's truthful or not. Anything that harms Islam is considered "backbiting".
Steve Coughlin explains it much better than I could. He refers to it as 'talebearing'. The entire video below is worth watching, but the part about "backbiting" (talebearing) starts around 21:45.