You can get similar results with a Speedball pen or something similar. I plan to make an instructable about that as well.
This is my first instructable, so please leave comments about how to improve it.
Step 1: Materials
Adobe Photoshop (I'm using CS3, but this should work with older versions)
Wacom Tablet, you won't be able to use a mouse, because you need pressure sensitivity
You probably could use a tablet PC too, but I'm using the Wacom setup.
Step 2: Brushes
Start by opening the Brushes palette. You can find it in the Window menu, or you can press F5.
In the Brushes palette, select the Brush Presets tab and choose a hard round brush in a small size (I'm using a 19 pixel brush and a 9 pixel brush)
Then, select the Shape Dynamics panel, make sure that its box is checked, and set the Size Jitter control to Pen Pressure.
Now that you have created the brush, save the preset by clicking on the icon in the lower right hand corner of the palette.
If you need to change tip sizes, use the Brush Tip Shape panel, not the Brush Preset panel.
Step 3: Create a New File
I'm going to use an 800x600 canvas with the presets from the Web menu. I don't plan on printing this, and the size is about right. If you want to print the final picture, choose an item from the Photo menu. The picture will be denser, since there are more pixels, so you may want to use a larger brush tip.
When you're done, Photoshop should have a canvas in the middle of the screen for you to draw on.
Step 4: Make a New Layer
You will need to show the Layers Palette, either by selecting it from the Window menu, or by pressing F7.
Then, click on the New Layer icon in the bottom right corner. Make sure that the new layer is highlighted before you begin drawing.
Step 5: Start Drawing!
I then like to draw lines coming out from the focal point, usually going downwards. I use the pressure modulation to make the lines go from narrow to wide. You can practice this on another layer until you feel comfortable with it.
Add as many lines as you like, and make them branch out from one another. I do plan on doing something else on the top part of the sphere, so I will leave that area clear.
Step 6: Adding a Line Shape
Start by drawing thin, somewhat straight lines from the top of the sphere. They should cross over each other, as this will make the end result look better.
Next, begin to draw rounded lines back and forth over the straight lines. Use a slightly larger line width for these. Start at the sphere and move up until you get near the top. I try to make the lines parallel the tips of the straight lines at the top.
The lines should probably get darker near the bottom, and should look as though they are coming out of the sphere.
Step 7: Add More Things Around the Focal Point
I've added the bubbles to give the piece a bit more variety.
I used a larger brush tip to add the designs on the edges.
In addition, I added the circle at the bottom to fill in that corner.
These elements are a few that I use regularly. You don't have to use them, but I think that they are a good place to start.
Step 8: A Few Final Touches
The waveform is a shape that I've been using a lot for this, but there are lots of other possibilities. Play around with the shapes and find one that works for you.
Step 9: Add a Background
To add the color, make a new layer between the background and drawing layers. Then use the Paint Bucket tool to fill in the color for the background.
I don't usually add any other color to the piece, but you could try adding some color behind it.
Step 10: Sign the Piece
When I sign, I usually make a new layer above the drawing layer, since it often takes me several tries to get my signature the way that I want it. I like to sign in the lower right hand corner.
Step 11: That's It, You're Done!
I'm interested in seeing what other people have done, so please post your designs in the comments
Also, this is my first Instructable, so I would appreciate constructive criticism about how to make my future ones better.