A crescent moon tutorial by Josh Smith (jspsfx). Done in Photoshop 7.
1. Create a new document. Width:500 Height:500. Create a new layer.
2. Get out your Elliptical Marquee tool.

3. Make a selection, have it take up most of the image. While making your selection, press shift to make it a perfect circle.

4. If you don't have the subtraction button clicked for your marquee tool already, do that... Confused? See following image, just click what the mouse is pointing to.

5. Still having your
original selection up, put your elliptical marquee tool up a little ways to the left, and drag it about a half inch from the right side of your selection.

Because you had the subtraction button clicked, it subtracted your second selection from the first, leaving you this crescent shape.
6. Select your Paint Bucket tool... Double click your foreground color from the color pallete, and set the Hex Color Code(?) to E6E4E4. If you don't get the whole color code thing, try to get your color to be around this shade of gray:

This'll be the base color for our moon.
Fill your selection with the paint bucket tool. You should have something like this so far:

7. Before doing anything else, Duplicate your crescent layer by draging the layer image into the New Layer button, or by going to Layer>Duplicate Layer.
8. Now we'll mess around with the layer styles for "Layer 1 Copy". Go to Bevel And Emboss in your blending options. To access these, either go to Layer>Layer Style>Blending Options, or click the little button with an f on it in your layer box, next to the Trash Can and New Layer buttons.
Here are the Bevel and Emboss settings you need to use:

Make sure you have all the numbers and options exactly like the image above.
Now your crescent moon should look like this:

9. To add a little bit of glow to our crescent, we'll do a gaussian blur on Layer 1. So, click layer one, and go to Filter>Blur>Guassian Blur, set the radius to 3.5
10. Create a new layer under Layer 1, and Layer 1 copy. To do this, click your
Background layer, and press the "New Layer" button. If you've been making your moon on a transparent canvas, just create a new layer and drag it beneath the two moon layers.
Press "d" on your keyboard to reset your colors to black and white.
Get your Paint Bucket tool and paint the layer black.
11. Right now, we're making stars. So, go up to Filter>Texture>Grain, and use the following settings:

12. The stars look like random dots, too pixely, so we'll add a glow to them. Go to Filter>Blur>Gaussian Blur, set the radius to 0.3
And I think that will wrap it all up for this tutorial. I've never made a crescent moon before, and I made it up as I went along. So I hope it's not too bad XP.
My Final Result, with some text: