I like a butter that is mostly shea butter but if my finished butter is going to have a chocolate fragrance i will add somecocoa butter, but only a little. Olive oil is too heavy for me so i stick to coconut oil.
Another good resource is Susan at http://swiftcraftymonkey.blogspot.ca/ She has lots of posts on her blog (free) and nice tutorials/workbooks for a modest fee. The tutorials cover anhydrous products (lip balms, salves), lotions, hair care products -- pretty much anything except for lye soap. I recommend her highly.