Plasma Effect

Start off by creating a simple shape on a new layer by using the Marguee Tool. Fill it with whatever color you like.

Next, use the Dodge Tool () and highlight the outside of the shape.

Then, duplicate the layer, rotate the shape, and change the Blending Mode to 'Screen' or 'Overlay' depending on what you like best.

Next apply the Filter>Distort>Wave Filter. Then, fade the the filter by going to Edit>Fade Wave Filter, if you are using PS 6+. In PS5.x, the option is under the Filter menu. Just turn down the opacity, and see what you like. If you want, you can also play around with the blending modes.

Finally, duplicate the original layer, and repeat changing the blending mode, rotating the shape, applying the wave filter, and then fading the wave filter, and so on. The last step is to apply the previous steps to the original layer so you don't see that shape that well. Also, I like to apply the wave filter again to layers that I've already applied the wave filter to and faded it already. You can get some greate effects, like the really transparent streaks coming off the plasma blob (not sure what to call this) as you can see on the left side of the effect. Experimentation is the key to getting this to look good. Don't be afraid to play around with blending modes and trying to apply other Distort filters.