Is there any method for extruding a 2D image into 3D? For instance, take a floor plan. Normally I would use the 2d floor plan as a texture map on a flat horizontal plan, and then use that as a guide for my walls, basically taking rectangles and scaling them to match the appropriate measurements for the wall, and then moving them into place. This method works fine, but I’m just wondering if there is any other more efficient method to accomplish this.
Use the SVG import to bring the floor plan in as a SVG curve, then you can use alt-c in object mode to convert to mesh. Illustrator exports as SVG, as well as Inkscape. 
bruxy’s published three very nice video tutorials on doing architecture in Blender. I believe he brings in the floor plan as a background image, but the rest of the building techniques are really worth seeing. He has a lot of tips and techniques for doing the tricky parts of building an architectural model for walk throughs or rendering. Highly recommended viewing.