I have been trying the HMB for about 10 days and it seems to help with mass, not sure yet with fat burning. What are your thoughts on its fat burning ability?

What is a good, safe fat burning supplement?

The more muscle mass you have the more calories your body burns, even when you are resting. So, any supplement that helps develop mass will help in the fat burning process.
Specific fat burning supplements include products like Twin Labs Hydroxycut and Sportpharma's Pyruvex. These are two of the best supplements in their respective category.
However, Hyroxycut falls into the "stimulant" category which, depending on your particular body, may or may not be safe for you to take.
Pyruvex on the other hand, relies on products that help in the fat mobilization process. Here is a short description about Pyruvex:

Sportpharma’s Pyruvex contains a new group of pyruvate compounds that have been shown to help your body loose fat up to 48% faster. Pyruvex combines these ultra pure ionically bonded pyruvates with other high powered fat fighters (L-Carnitine, ChromeMate), and Pyruvex is sodium free, unlike many older pyruvate products. Calcium and Potassium Pyruvate have also been shown to increase lean muscle mass by up to 21%, and enhance performance by increasing muscular endurance up to 20%.