This technique attempts to simulate infrared photography, where green foliage looks white and blue skies look close to black. This one will take a little bit of experimenting on your part, but with a bit of effort you can get some interesting results.
Here's the original photo.
Depending on your photo, you may want to add more overall saturation to the photo, and specifically more saturation to the greens. Here I clicked on the Create New Adjustment Layer icon at the bottom of the Layers palette and added a Hue/Saturation adjustment layer.
In the Hue/Saturation dialog, I added some saturation to the Master (all colors), and then chose Greens from the Edit pop-up menu and pumped up the saturation slider for it, too.
Next, click back on your Background layer and add a Channel Mixer adjustment layer. Turn on the Monochrome checkbox and move the Source Channels sliders, using the rough guideline of having the three amounts add up to approximately 200.
Click on your Background layer again, and press D to make sure your Foreground and Background colors are the default black and white. Then add a Gradient Map adjustment layer. Click on the gradient thumbnail in the Gradient Map dialog to open the Gradient Editor. Make sure the top-left gradient (Foreground to Background) is selected.
Press-and-hold the Option key (PC: Alt key) while you click-and-drag the right-hand (white) color stop to copy it and create another white color stop.
Use the same method to create another white color stop, and then double-click on the far right color stop to bring up the Color Picker. Change the color stop to black, as shown here.
As you make these changes to the gradient, you can see the effects on your photo.
To further edit the effects of the gradient map, click on one of the white color stops and you'll see a small diamond between the two color stops. Click-and-drag on the diamond to change the distance of the blend between the two color stops.
Here's the result I got after tweaking the position of the white color stops and the diamonds.
Control-click (PC: Right-click) on the Gradient Map adjustment layer and choose Blending Options. Press-and-hold the Option key (PC: Alt key) and click on the black Underlying Layer Blend If slider. Drag the right side of the black slider to the right, approximately halfway, until some of the black starts to show through.
Here's another example with the same technique applied.
Here I clicked on the original Background layer and, from the Select menu, chose Color Range, where I selected Highlights. I added a new layer on top of the layer stack, filled the selection with white, and changed the layer blend mode to Soft Light.
Variation 1: Highlights filled with white, set to Soft Light