This is perhaps the most ghetto picture I have ever taken.
To take macro pictures on an SLR you have to have an expensive macro lens, right? Wrong. I took this one with just my 18-55mm kit lens and my 50mm prime.
What you do this this - put one lens on the camera (preferably something with a bit of an enlargement factor - I used my lens' longest focal length of 55mm), and then take your 50mm prime and hold it backwards against the lens on your camera. Be very careful not to grate the glass against anything as this will scratch it!
You then look through the viewfinder and get veeeery close until your subject is in focus. If you have a long enough focal length all you will get is a funky vignette (the vignette in this photo is natural btw), and if it isn't then you will have a funky circle around the whole picture and then a vignette inside that instead.