Amphetamines:

What are its short-term effects?
Short-term effects include increased talkativeness, increased aggressiveness, increased breathing rate, increased heart rate, increased blood pressure, reduced appetite, dilated pupils, visual hallucinations, auditory hallucinations, compulsive, repetitive action. Other effects of large does can include fever and sweating, dry mouth, headache, paleness, blurred vision, dizziness, irregular heartbeat, tremors, loss of coordination, collapse.

What are its long-term effects?
Possible long-term effects include tolerance and dependence, violence and aggression, malnutrition due to suppression of appetite. Amphetamines are addictive.

Barbiturates:

What are its short-term effects?
Slurred speech, shallow breathing, sluggishness, fatigue, disorientation, lack of coordination, dilated pupils. Barbiturates mimic alcohol inebriation causing mild euphoria, disinhibition, relief of anxiety and sleepiness. Higher doses cause impairment of memory, judgment and coordination, irritability, paranoid and suicidal ideation.

What are its long-term effects?
Tolerance develops quickly and larger doses are used, increasing the danger of an overdose. In an overdose or when taken with other drugs like alcohol, death is due to depression of the respiratory center in the brain. Withdrawal symptoms: Include tremors, elevated blood pressure and pulse, sweating, and possible seizures.

Marijuana:

What are its short-term effects?
Short-term effects of marijuana include problems with memory and learning, distorted perception (sights, sounds, time, touch), trouble with thinking and problem solving, loss of motor coordination, increased heart rate, and anxiety. These effects are even greater when other drugs are mixed with marijuana. A user may also experience dry mouth and throat.

What are its long-term effects?
Marijuana smoke contains some of the same cancer-causing compounds as tobacco, sometimes in higher concentrations. Studies show that someone who smokes may be taking in as many cancer-causing chemicals as someone who smokes a full pack of cigarettes every day. five joints per week

Information from: http://www.drugfreeamerica.org/