Resources
FreePSDFiles has a great 3D map of the USA. The 300 dpi PSD file is fully editable, with each state having its own layer—allowing you to highlight individual states as well as add a popover (as seen in the screenshot above).
Adobe Photoshop
Another image font, this time a collection of bird feathers from Manuel Persa. This collection is stunning in detail. You can download the layered PSD file here.
Each letter of the feather type alphabet is on its own layer, and at 30 x 40 inches at 300 dpi overall, the artwork is perfectly usable for commercial printing
Resources
Resources
Resources
If you’re designing apps or comps for the iPhone 4 with a retina display (640×960), you’ll find this collection of iPhone 4 GUI elements quite helpful. This fully layered Photoshop file contains all the elements you need, and weighs-in at a whopping 4074×2986 pixels and 63MB in size.
Adobe InDesign
I generally only save image files as layered PSD files, it saves space on my hard drive and a load of time when making edits. Another advantage is that you can control which layers show up after you place them in your Adobe InDesign document.
Once you place your PSD file in your InDesign document, select it and choose Object>Object Layer Options… In the dialog box that comes up you’ll see a list of the layers in the placed PSD file. You can simply click the icon next to the layer name to turn it on and off.
If you choose, you can check the Preview checkbox to have the preview image show the changes. I generally leave Previews off because it slows down InDesign tremendously – especially with large layered files. It’s extremely helpful if you name your layers in Photoshop so you know what they are after you place the PSD in your InDesign document.
Adobe Photoshop
Teehan+lax has made available a layered Photoshop file containing all the iPad GUI elements you could possibly need. The file is built using vectors, so it’s all still fully editable. If you need to mock up something quickly for a client, this layered Photoshop file will certainly do the trick.
You can download the 24MB layered Photoshop file here.
And if you have the need for an iPhone version, grab the 9MB layered Photoshop file here.
Adobe Photoshop
If you want to open a layered Photoshop file as a flattened image you can save time by going to the Open dialog box in Photoshop and selecting your file. Hold down the Shift and Option keys and hit open. You will be presented with a dialog box asking if you wish to Read the Composite Data Instead. Hit OK and you will have a flattened version of your file opened instead of the layered version. This key-combination works while double clicking a file in the Finder as well.
Resources
I recently had the need to use a nice clean image of a smartphone. I began searching through the numerous images found via Google and eventually came across this freely available layered Photoshop file of a BlackBerry – just what I was looking for from a user over at DeviantArt. 
The 6.2 MB download expands to a 15 MB PSD image containing, well, a ton of layers – allowing you to customize the heck out of it.