This tutorial is 5 steps and has a difficulty of Intermediate. This tutorial will show you from start to finish how to make a nuclear waste texture. The result is pictured below.
Step 0

     1. First create a new document, I'm going to use a 300 x 300 pixel image, you can use whatever size document you want though.

     2. Now, you need to reset the colors by pressing D and then X.

     3. Go to Filter > Render > Clouds, now you need to go to Filter > Render > Difference Clouds. After that press Ctrl + F about 6 - 8 times or until you get something similar to the image pictured below.
Step 3

     4. Now you need to go to Filter > Stylize > Find Edges. Now press Ctrl + U To bring up the Hue/Saturation. Check Colorize, and now set the Hue to 100, and the Saturation to 60, now press ok and you should now have something similar to the image pictured below.
Step 4

     5. You now need to go to Layer > Duplicate Layer . . . and just press ok. Do that one more time and fill both of the layers you just created with black. Make sure that the layer that is green is beneath the other 2 layers. For the new black layers, set their layer styles both to Overlay from the layers window which you can bring up by going to Window > Layers. On the top of that window to the left of opacity is where you change the layer style. Your all done and your finished product should look similar to the below image. You can obviously use your own settings for stuff, but this is just what looked cool for this I thought.
Step 5