You don't need a full gym, massive amounts of space and all the weights in the world to get an effective workout i. Sure, it's much more convenient, but if you're in a jam, here's a full body circuit using a single 45lb. plate. (or 25lb/35lb - depending on strength)
Complete as many reps as possible. [failure/exhaustion]
Complete five rounds.
Rest 120 seconds in between rounds.
Add all your reps for a score.
MOVE ONE: Overhead Squat
Press the plate overhead and stand with your feet in traditional squat position. Attempt to "stand tall" while squating.
MOVE TWO: Clean to Overhead Press
Hold the plate in front of your with your hands on each side of the plate. Raise the plate up from your waist to your shoulders then explode upwards into a press. (your hands may change positioning slightly due to the shape of the plate)
MOVE THREE: Single Arm Bent-Over Row
Hold the plate with a neutral grip in one arm with other arm to your side. Complete as many reps as possible and switch sides.
MOVE FOUR: Traditional Push Ups
Hit the floor and complete as many push ups as possible.
MOVE FIVE: Floor Presses [for speed]
After completing your push ups your body will be a bit taxed - grab the plate and "press" just like a bench press but from the floor. Complete as many reps as you can, as fast as you can.
MOVE SIX: Russian Twists
Hop up into a seated position with the plate to your side in both hands. Slightly lean back and rotate the plate from one side of yuor body to the other while touching the ground on each side.