As a victim of a break and enter two years ago I can tell you that one of the most awful things to experience is coming home to a door that's been kicked in and discovering that all of your most valuable possessions have been stolen.
The truth is most burgulars can kick in a door with one well-placed kick or body slam close to the deadbolt and handle area, which can split the door apart, split the door jam apart, or even pull the hinges out of the frame.
Here are a few quick, effective and cheap solutions you can do to beef up the security of your existing entrance doors, making them much more difficult to break through. Even the sight of some of these will discourage would-be burgulars from even trying to break in and move on to a less secure house.
1) Reinforce the door with a metal reinforcement wrap.
2) Replace the flimsy striker plate with a heavy duty striker plate.
3) Replace hinge and striker plate screws with 3 inch long screws that go in to the underlying stud, not just the door jam.