You can even experiment with different coloured strips of cellophane taped together to cover the lens for some fun effects.Play around with the amount, positioning and thickness of cellophane around the lens to get different looks.Sure you might get some funny looks when using these tools, but it's all in the name of having fun and experimenting with your photography.
A spare pair of stockings can make for a DIY soft-focus filter.
Simply slip the stocking over your lens and pull taut, then secure around the barrel with a rubber band.
It's even possible to get a tilt-shift effect with two streaks either side of the centre of the lens.
For this effect you can also use a cheap skylight or UV filter so you can rotate the plastic film, or if you're really daring and don't mind cleaning up later on, smear the Vaseline on the filter itself.
Also consider using transparency film and adding colour with markers, then holding this in front of the lens.
Bear in mind that by covering the lens with any object, you will lose some image sharpness.
Open up the aperture (by using a small f-number) to blur the background and create a shallow depth of field effect.
Then, you can rotate the entire image 180 degrees in post-processing to turn the refracted image right way up, and the background is turned upside down. A pair of sunglasses can achieve a similar effect by cutting down on the glare entering the camera and altering the properties of the light.
Make sure to attach the sticks using a non-marking, easily removable tape such as duct tape so you don't damage your lens.