For this you will have to have a basic understanding of gimp, but you don't need a lot of experience.
This was originally a PhotoShop tutorial, but it was really easy for me to convert it. It was at http://www.photoshopgurus.com/beginner/ ... effect.pdf
This is the final result/s (or something like it) click it for bigger version:

This takes about 10 minutes for first try, and after you do it enough it can be done in about 3 minutes.
Step 1: Make a new image, white background, but make sure it is a square. If you use a rectangle, it adds an extra step. For this tutorial I will use 300x300.
Step 2: From the left, select about 3/4 of the image.

Step 3: Fill the selection with black, and then deselect (shift+ctrl+a).
Step 4: Go to Filters-Distorts-Wind...
Step 5: For 300x300, choose these options.

For another size, play around to get about the same thing. Once that is set, press OK.
Step 6: Go to Filters-Blur-Motion Blur. Choose about these settings for 300x300. It should just be touching the opposite side. You Must leave the Angle at 0.

After you have the settings correct, press OK.

Step 7: Go to Layer-Transform-Rotate 90 Degrees CCW. If you used a rectangle, you will have to scale the layer to the right size of the image here.
Step 8: Go to Filters-Distorts-Polar Coords... and play around with the settings, but you MUST leave To Polar Checked
Step 9: Press OK and you are done. You can play around with colors in the other steps and get some cool effects.
This is another example of one with colors. You can see it behind the "R" It was for a friend, if you are wondering.

Cool , very useful , thanks

How did you make the black spike ball? It looks a lot better.

I inverted the colors after I finished.

when I invert it it still has the square thingy in the middle. I want it to be thinner in the center like yours.

Well, you basically just have to play around with the settings.

I know this is offtopic but how do you create a post?

Thanks a lot for this tut. This is the first thing I made in GIMP. Nice easy to follow tutorial! Keep up the good work!

thought a good effect, couldnt you jsut make a large spikey brush?

Ummm .. couldn't you just create a supernova in the light effects ( or something like that )

This is what I made with your tut:



Thanks for the help!