I got this only by starting out with gaussian generated noise and then using the render filters that already come with Photoshop. Only the cloud filter had to go on another layer. Looks like rough-hewn stone, huh?

If you keep doing different layers and playing around with channels and mixers, you can get all kinds of interesting textures.

---EDIT---
Found a link for another freebie goodie for bricks. In case you need to save money or don't know a quick way to do it procedurally in other software:
http://www.acmebrick.com/md/index.htm

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Barbequed Pixels?

Your friendly neighborhood Wings3D nut.
Also feel free to browse my freebies at ShareCG.
There might be something worth downloading.