There's something about tiny things that is just inherently fascinating. Tilt-shift photography is a great example of how making large, real-life objects look miniature can create beautiful art.
Tilt-shift is a kind of photography that manipulates focus and depth-of-field to yield photos that have selective focus, often mimicking a miniature model. The effect can be achieved with special tilt-shift lenses, but you can also fake the effect in post-production via Photoshop.
See also: 10 Terrific Tilt-Shift iPhone Photos
Here's a step-by-step tutorial on how to create tilt-shift miniature fakes with just a few effects in Photoshop.
This is possibly the most important step. Choosing the right photo will ensure that your final image has maximum effect by starting off on the right foot.
Tilt-shift photography tends to work best for photos that have a wide view and are taken from higher ground. The photo doesn't necessarily have to be an aerial shot, but it should be something that is composed of many small parts that make up a whole. You should be able to envision how your photo might be manipulated to look like a miniature model, even before its Photoshop transformation.
For this tutorial, we're using a shot of Barcelona taken from the hill of El Carmel:

An optional step, you can pre-edit your photo in Photoshop Camera Raw to prep it before adding additional effects. To do this, open up the Open menu in Photoshop, select your file and then select Camera Raw in the Format drop-down menu.

From here, you can play around with adjustments until you're satisfied with your photo. Remember, the idea is to make it look more toy-like to look like a miniature model. The first step is to increase the clarity of the photo so your photo will have crisp edges. You can give it a hefty increase in clarity, but be cautious that it doesn't look too fake. Then, increase the brightness, contrast, vibrance and saturation of your photo as needed. Once you're satisfied, click Save Image and then Done to exit Camera Raw.

Since our photo already has a fair number of colors and looks close enough to a miniature model, we'll forgo the Camera Raw step.
Open up your photo in Photoshop and switch to Quick Mask mode. You can do this by either hitting the Q key on your keyboard or clicking on the Quick Mask mode button at the bottom of your tool box menu. This will basically "mask" your selected areas from whatever effects you apply next.

Select the Gradient tool, which looks like a rectangle with a gradient across it. You can also just hit G on your keyboard.

Using the Gradient tool, draw a vertical, perpendicular line. This is a tricky step. You want to start the line in an area that you want to be in focus, and then end the line in an area that you want to be out of focus.
For best effects, your in-focus area should be something closer to you, rather than farther. In the photo below, we've outlined in red the line we drew. Note how it starts with the in-focus and closer white house and ends where the buildings are less distinct and out of focus.

In your options bar, make sure you have the fourth choice selected, which is the Reflected Gradient. This will make a gradient that has a mirror-effect.

After you draw your line, there should be a red bar over the area that will be in focus. It usually takes a few tries to get this exactly the way you want it, so play around with the gradient until you're satisfied.

Click on the Quick Mask mode button again to return to Standard Mode, or simply hit the Q button on your keyboard again. Now, you should see a series of marching ants selecting the area that you don't want to be in focus.
Remember, the Quick Mask mode puts a "mask" over the effects you're about to add next, and we want to put a lens blur on the selected area. If you aren't satisfied with your selection, undo and repeat the last step until you've picked the perfect area to be in focus.

Once you're satisfied with your selection, go to Filter > Blur > Lens Blur to put a lens blur effect on the area you've selected.

A new window will open, and here you can preview your effect before applying it. You can adjust how blurry you want the background to be, but just be careful to not make it look too fake by making a sudden jump from in-focus to out of focus.
Once you're satisfied with the effect, click OK to accept and exit the lens blur window.

Get rid of the marching ants by deselecting your selected parts under Select > Deselect.

Now it's time to make the photo look more model-like by adjusting the color and contrast of the photo. To adjust saturation, go to Image > Adjustments > Hue/Saturation.

Slowly increase the saturation of the photo until it looks more toy-like. Again, the idea is to lay on the effect in an amount that tricks the eye, but not too much that it looks fake and unbelievable. Click OK when you're satisfied with the effect.

Adjust the contrast of the photo by accessing the Curves panel. Go to Image > Adjustments > Curves.

Making a slight S-curve will increase the contrast of your photo to make it look even more toy-like. Play around with curves until you have a desired effect, then click OK to accept the effect and exit the panel.

This is the final product of a miniature Barcelona. Play around with the steps above and show us some of your own creations in the comments below.
Images: Mashable, Denise Lu