This is a very simple Matrix effect, using a few simple steps. This is done in photoshop CS5, but can be done using the same filters and methods, in any editng suite.

This is the base image I started with, and these are the steps.

Firstly, download a matrix code image (google it, and you will find loads of free to use images of code). I used this one

First of all, duplicate your base image, in a new layer, and apply the "glowing edges" filter, until you have something like this:

Yours will be in colour, so we now have to make it all green. Simply go to Image/adjustments/Hue-Sat, and tick the "colourise" box. Then adjust the hue, until you get the desired green colour, and click OK.

Now duplicate this layer, and add a "diffuse glow" filter, and adjust until the highlights just begin to blow, like this:

Now to add your raining code. This will need a layer for each main flat surface. In this case only 2 are needed. One for grass/ground, and another for background. Using your "Matrix code" image, distort the image to match any flat surfaces, and set it to a blending mode of "Lighten". Also erease the code where there are any subjects or detail, using a brush at about 20% opacity. This doesn't have to be accurate, and was done very quickly (as you can see). Use 100% opacity, where you don't want any code to spoil detail Your code layers will look something like this:

Setting to "Lighten" blending mode, will make the black vanish, and just leave the raining code behind. Now you can adjust the code layers opacity to taste, and increase saturation of whole image, to give a brighter green colour.

The end result is this