Diet pills:
Most diet pills (OTC, in any case) are not proven effective, and sometimes are not even proven safe. (now-illegal, ephedra for example) They can have any variety of intended effects such as appetite suppression, metabolism/energy boosts. Most functional diet pills contain caffeine, which will boost your metabolism for a certain amount of time, but it can also cause you to retain water. And we all hate retaining water, which is probably how we get addicted to

Diuretics:
Diuretics are interesting little creatures. They force water out of your body. Abuse of them often results in severe dehydration and death.

Laxatives:
These make the bowels move. Often after a binge, we may pop a few of these. Some of us realize, and some don't realize that taking laxatives with a binge will not stop your body from absorbing the calories. It simply (and sometimes painfully) pushes out the leftovers, after all the calories have been burned. Laxative abuse will eventually lead to incontinence (inability to hold waste in), possible dehydration/death, and dependency. Laxative dependency is terrible, in that you can no longer even have a bowel movement without taking a fistful of laxatives.

Safe, and just as effective alternatives:

Diet Pills:
Diet sodas and coffee (with no calorie sweeteners. be careful of aspartame- it causes cancer in 3% of lab rats) contain caffeine just like diet pills, which will boost your metabolism. Plus a warm drink like coffee will expand your digestive tract and cause you to feel fuller. (appetite suppressant)

Diuretics:(this goes for diet pills too)
Green tea. Green tea will not only boost your metabolism, but it has a diuretic effect. Be careful about adding sweeteners or lemon. Lemon will cancel out any diuretic effects of green tea because it will cause you to retain.

Laxatives:
Yes, I even have an alternative for these. It's not painful, just tastes bad. In the morning, on an empty stomach prepare a quart (or one liter) of water with two teaspoons of salt (sea salt or kosher salt- no iodized stuff). Drink the entire thing (as quickly as possible) and do your best to keep it down. (all that fluid coupled with the awful taste is sometimes a lot to handle) Within two hours, it should find its way all the way through your system and will clean out most (if not all) of the gunk in your large intestines. Works exactly like a laxative, but without the dangers.

Please remember to drink LOTS of water. EDs tend to forget how easily we become dehydrated. Especially when we take diuretics/laxatives. Drinking too much water is also bad-- you can get water poisoning or dangerously throw your electrolytes out of balance. Try drinking a sports drink like gatorade (50 cals/serving as opposed to a pepsi at 160cals/serving) to help even out your electrolytes. Electrolyte imbalances are a cause of dizziness and fainting. The last thing you want during that English final is to pass out.