What groups of items in Rage are completely unusable and safe to sell?

The first time I was able to sell collected items in Rage, I unloaded what I thought was junk to the vendor. As it turns out, one of the items is considered an ingredient to be used to craft something. Is there a comprehensive list of items that are safe to sell, or vice-versa, things that I should hold onto? I'm not sure at this point which of these lists would be shorter. Some of the descriptions on items do make it obvious to sell, while others aren't exact.

Items I've found safe to sell so far:

• Books
• Cans of Food
• Rusty Toolbox

Items I had sold, but turns out are Ingredients:

• Cloth Rags

If you look in the description you should see a small emblem. If its a gear, you can use it. If it has a dollar sign, sell it. =]