Here are some little exercise routines for people who prefer not to go to the gym!

Body Circuits (taken from NerdFitness):
This is a basic body weight circuit. You do each exercise in succession and once you've finished all the exercises, do the circuit again. I'm aiming for 3 circuits.

Start by WARMING UP. (5 mins of jogging, skipping, running up stairs etc)
20 body weight squats
10 push ups
20 lunges (10 each side)
20 dumbbell rows (10 each side) - use a gallon milk jug if you don't have dumbbells!
15 second plank
30 jumping jacks


Interval Training (also taken from NerdFitness)
Interval training is when you vary your speeds and intensity throughout a shorter run. Here's how you do it.
Start by WARMING UP. (5 mins of jogging, skipping, running up stairs etc)

30 seconds of increased pace (70% maximum effort) followed by 2 minutes at decreased pace.
30 seconds of increased pace (75% maximum effort) followed by 2 minutes at decreased pace.
30 seconds of increased pace (80% maximum effort) followed by 2 minutes at decreased pace.
30 seconds of increased pace (85% maximum effort) followed by 2 minutes at decreased pace.
30 seconds of increased pace (90% maximum effort) followed by 2 minutes at decreased pace.
30 seconds of increased pace (95% maximum effort) followed by 2 minutes at decreased pace.
30 seconds of increased pace (100% maximum effort) followed by 2 minutes at decreased pace.

5 minutes of light jogging and stretching. When you stretch, your muscles expand, allowing the nutrients you are about to eat fill in the gaps left empty from exercise. Also it keeps your muscles loose, so less chance for injury.
It's also possible to do these intervals on a treadmill or elliptical trainer.