If you're looking to burn fat, you don't want to go crazy, super high heartrates don't burn fat, they just build cardiovascular health. My brothers girlfriend is taking a nutrition/exercise class, and they said 30 minutes of cardio, with a HR of 145, will burn calories for 5 hours afterwards.
Instead of finding different exercises, learn about how to do them properly. Don't cheat reps, swing your body, etc. Also, you need to be mentally there for your workouts. Lifting weights and thinking about something else won't give you a good workout. You want to be intense in the last reps, you want to be breathing hard, and really struggling. If you're not, you're wasting your time. Breathing patterns are important as well. Always breath in when you're not under load, and blow out under load.
Start with what you know, I'm sure youtube is loaded with videos on how to perform different exercises and the proper methods. In general, free weights work you harder then guided machines. However, there isn't anything wrong with using a machine, as long as it's done properly.
SheepStar