Anyone know any good sites about substance abuse?

i just recently got caught with weed and i have to write a 3 page essay on substance abuse,anyone know any good sites for that? also does anyone know if people can get drug tested at a drug seminar (idk how to spell it) cause i got a 90 day period of prohbation and my last test was on april 25th and my prohbation officer is sending me to a drug seminar tommorrow.im 15 btw