Result:
Click here to view!

1. First open up photoshop, with whatever size you want, i will be using 640x480. Now press X to make your foreground color white and then get the paint bucket tool (G) and on your first layer (which is going to be your BG layer) fill your canvas white.

2. Next make a new layer and get your Horizontal type tool (T)
Image

3.And now set your font as Arial Black and type in your text. It is recommended that you type your text all in caps.
Image

4. Now make another new layer and make a selection using the Rectangular Marquee Tool (M) just about 30 pixels away from the text, try to make it match the following screen shot:
Image

5. Now after you've made the selection, still keeping the selection, right click anywhere inside the selection and a menu will come up, click on 'Stroke'. And now a window will come up, use the following settings:
Image

6. Now after you've finished with the settings, click OK and now merge the selection layer with the text layer. to do this select the upper top most layer, which should be the selection layer and then go to Layer > Merge Layers. ( Ctrl + E)
Image

7. Now its time to get grungey! select the merged layer and click the eraser tool (E). Now you will need some grunge scratch brushes, you may use a pack i have already prepared for you:
AK-ScratchBrushes download
Now back to topic, with the eraser tool and using the brushes provided start to brush up your image by erasing it! Remember don't erase too much, you want to erase just as much so that it looks like a grunged up stamp and is still easy to read.
Image

8. After you have finished grunging it up, press ctrl+T or go to Edit > Free transform. And then rotate it to your liking, this is how i did mine:
Image

9. Now duplicate the layer, ctrl+J or right click on the layer and then click Duplicate layer. And on the duplicated layer set the blending mode to Soft Light. And there you have it! Now you can use this stamp as a logo, a brush, a pattern or anything of your imagination!

This concludes our tutorial, you should have something similar to this:
Click here to view!

Download this tutorials .PSD file here.