I've been asked a few times where I get my noise/pattern textures. So I wanted to write a little extra post all about them.
I use a combination of online generators and self-made textures.

This generator covers a big variety of textures, not just seamless noise, but also flares/ fire/caustics/ magic circles.

This generator is meant for backgrounds on webpages, but it has a few nice noise samples and lets you layer multiple textures over eachother.

This seamless generator lets you choose from a few presets and also has a button for the editor where you can see and edit the code behind the texture.
Right-click the small thumbnail in the lower left corner to open in new tab for saving

This one is a bit simple, but it has a nice fractalnoise setting and color customisation,
It needs a run through Photoshop or similar to make it seamless though.
You can also draw your own effects. I'm using Photoshop, but as a free alternative, Krita has a wrap-around mode that let's you easily make tiling textures.
Offset

One way of making something seamless is to use a Filter>Other>Offset and set it to half the texture size, then drawing over the seams and repeating.
This is works but can take some time. It's the best way for handpainted textures though.
There is a faster way
Seamless Photoshop Plugin

The Orange Box has a free FX-plugin that makes this easier. First install the FX-Box , then install the Seamless Texture Generator
Go to WIndow>Extensions>FX-Box and select the seamless plugin.

The plugin offsets the texture, then creates a sof circle of the original and lays it on top of the offset, It won't work for all textures, but it's pretty good for noise/weird patterns that don't need to look realistic.
If you're looking for fancy magic spell effects, try out fractal programs.

Apophys (You can find downloads on Google, can't find the official site anymore)
Apophys gives you a lot of plugins and options, but you really need some help to get started here, here is a tutorial for a basic spell-like effect

For the Incendia suite, you can get some nice results just playing with the options from the Quilts program
Bunch of textures using methods/links from this post:










