I have a friend who always used to say "There are no free lunches!" What he meant was that you can't expect to find free stuff and shortcuts that actually work. A few months ago, someone from work emailed me to ask about whether or not I thought there were any weight loss supplements that work. So I responded...(can you tell I'm busy this week?)
What I have found over the years is that there isn't one supplement that makes "the" difference for weight loss. There are many supplements that support metabolism, and this is usually specific to an individual's needs. For example, some people find Chlorella supplements help with digestion and energy levels, and this ultimately helps them lose weight (maybe indirectly).
Other people have found that green tea supplements have a made a difference, but I don't have a lot of faith in this method because green tea is not regulated (different brands have different amounts of the EGCG that promotes healthy metabolism).
Then there are those ads you see all over the internet for the natural solutions---right now I keep seeing the acai berry pills being sold in conjunction with colon cleansing pills. It is true that both of those things could promote weight loss, but the company selling them are roping people into automatic monthly refills charging $89 to your credit card each month!
There are also pills (i.e. Jet Fuel, Hydroxycut, etc) that say they promote weight loss. Some of them are stimulants, which have not been approved by the FDA, so I don't recommend these. In the past, things like ephedra worked, but were also potentially dangerous.
I think the bottom line is that there is no one thing you can take to cause weight loss safely (especially if you don't plan to take it for the rest of your life to maintain the results). In the end, having a healthy diet with lots of vegetables and greens and lean proteins is both the healthiest for all of your body systems and for your weight.
I usually recommend people try and change small things gradually about their diet in order for it to become a lifestyle, and integrate "superfoods" as much as possible. My favorites are goji berries, raw cacao (but this has a very strong taste, so ease it into things), blueberries, raw pumpkin seeds, and all green vegetables.