After looking through the tutorials and such around, there was a particular look of a dungeon I wanted and finally I decided to take a crack at making my own tutorial. What follows I hope is helpful.

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Fast Dungeons In Photoshop Tutorial:

Setup: Create a new document, 8.5x11, 300dpi, background transparent.
1) Select your first layer and Rename it Background, Filter>Render>Clouds; then Filter>Stylize Emboss; then Image>Adjustment>Hue and Saturation - select Colorize.
2) Duplicate this layer and name it Walls
3) Create a new layer and name it FloorPlan
4) (Optional) Create a new layer and name it Grid
5) Move the Grid layer between your Background layer and Walls.
6) Select your Walls layer, Add Layer Style>Stroke: Size: 5, Position: Outside, Blend mode: Overlay, Color: Black
7) Select your FloorPlan layer, Add Layer Style> Stroke: Size: 50, Position: Outside, Blend mode: Overlay, Fill Type: Pattern (select the pattern you want to appear outside the walls (for this tutorial I used a crosshatch pattern).
With the FloorPlan layer still selected, set the layers Fill property to 0%

**At this point you should have a layer structure from Top to Bottom of FloorPlan, Walls, Grid, Background. (If you are planning on using this method for multiple dungeons, save the file before going further.

9) Now paint your dungeon on the floor plan layer, you will notice that only the border of the rooms and walls appear. You can also you the Marquee tool to create rooms and halls, to do so, create the room with the Marquee tool, then right click>Fill:White. You can overlap your halls, rooms etc.
10) Use the Magic Wand tool and select inside your floor plan.
11) Select your Walls Layer (the selection of your floorplan should still be active) and hit Ctrl-X (or Edit>Cut). And your done. If you want to add additional rooms to the floor plan just repeat steps 9-11.

Extra: You remember we created a Grid layer earlier that at the moment is doing nothing.
You can create a transparent grid to fill in here. Create a new project: 75x75 (for a 4sq per inch grid, 60x60 for a 5sq per inch grid). Fill it with Black, then Ctrl +A to select all. Use your arrow keys to move the selection 1px down and 1px right, Ctrl+X, then Edit>Define Pattern. (Credit for this goes to: )

Once you have the pattern saved, you can select your Grid Layer then Edit>Fill: Pattern (select the transparent grid you just defined) and there's your grid. For purely style I set the blend mode to the Grid layer to Overlay.

Additionally: Create a new layer, Rename it Dressing, Set the layer blend mode to Overlay. Then move the layer to between the Grid and Wall layers. Use this layer to paint on any dressings you would like, doors, statues, etc.
Those in the example map are from the brush pack I made for Photoshop that you can find here: