One thing that comes up a lot for me while building websites based off Photoshop designs, is that I need the ability to quickly and easily edit a layer by itself, as its own document, and then be able to export that file by itself as well. So how can we do that? I am using Photoshop CS5 though this may work the same in other versions. Here is what you do.
1. Right click the layer you wish to use.
2. Click, “Duplicate Layer…”
3. From the “Destination” drop-down menu, select “New.”
4. Your document will now open in a new window of its own, but probably with the original document size. To cut it down to just the size of that layer, Navigate to “Image” on the top menu.
5. Select, “Trim…”
6. I usually just leave at the default settings, but make sure “Based on Transparent Pixels” is selected. Click “OK”.”
That’s it! You can now work with that document however you wish. You can edit it or export it in any way. You can also select more than one layer or even groups from the first step and follow the same process to get them in a new document. Enjoy!