I've gotten my hands on an HLSL .fx shader from Microsoft that distorts (ripple-style) a texture given a set of parameters. I've been playing around with the .fx file for a little to make it a little more customized. However, this shader only distorts once...

I want to be able to add more then 1 ripple effect to my scene at any given moment and I also have plans for adding 2 more pixel shaders. At the moment this doesn't seem within my reach because I can not figure out how to utilize more then 1 pixel shader per frame. I done loads of googling to no avail, so I'm really just asking how do I apply more than 1 shader at a time?

Are you talking about a post-process shader, or something applied to a model? It sounds like a post-process to me, in which case Aaron Bolyard is correct.

I found this code, related to a ripple:

If your code is similar to that, then you have the two options posted by Aaron. Either write more stuff inside the existing shader, or do multiple passes:

technique PostInvert 
{
  pass P0
  {
    PixelShader = compile ps_2_0 Invert();
  }
        pass P1
  {
    PixelShader = compile ps_2_0 DoSomeOtherShader();
  }
}

The C# side of things is like this:

for (int ps = 0; ps < ppShader.CurrentTechnique.Passes.Count; ps++)
            {
                ppShader.CurrentTechnique.Passes[ps].Begin();
                mySpriteBatch.Draw(PPTarget.GetTexture(), Vector2.Zero, Color.White);
                ppShader.CurrentTechnique.Passes[ps].End();
            }

You can also just use multiple effects, it isn't much different than doing multiple passes with the same effect.

Use a RenderTarget with Vector2 data instead of RGBA to store distortion data, then just distort everything once using that RenderTarget as an distortion data input texture (just use sampler2D = sampler_state { texture = <my_texture> }; and tex2D with the current UV). There are tutorials on doing that somewhere (there was one on ZiggyWare, but it seems it has been down for some time now). You could also (possibly) use 8bit R and G channels to store x and y distortions respectively.

Well right now I have this for drawing the ripples in my draw method:

As you may notice, my intentions were to have the ripple effect be drawn for all the items in the list "Ripples". But that is not what happened. I have tried using multiple passes and using arrays for the parameters but that did not work either.

So how do I "update" the texture that I am passing to the shader?

I've tried using multiple render targets, but that is not an option because it really eats up video memory

Okay, I'm trying to utilize ResolveTexture2D, and this what I've got:

However, the screen is just black when ripples are supposed to be drawn.