18mm on your kit lens not wide enough?

For this workflow you need at least PS CC and ACR 9.
It might be possible with other software, but this is what I use.
You can also use tripod, but it's not a requirement.

Procedure:
>set your lens to its widest angle (e.g. 18mm for a kit lens)
>set your file format to raw
>set your camera to full manual
>use the exact same settings for each photo (shutter speed, aperture, ISO, etc.)
>take 9 photos in a 3x3 grid formation, lock the focus while taking photos (don't refocus)
>make sure each photo overlaps with adjacent ones by at least 1/4
>drag and drop all 9 files into Photoshop, they will open up in ACR
>select all photos in the Filmstrip, right click on one of them and select Merge to Panorama
>mess with the settings in Panorama Merge window until satisfied with merge results
>click Merge, name the file, and merged photo will appear at the bottom of Filmstrip
>also, the merged photo will be saved as DNG file in the same folder as source files
>click Done to close the ACR (there's a bug where you can't immediately open the merged file in PS)
>drag and drop the just created DNG file into Photoshop and edit as you would any other raw

So it's basically a panorama, only with a fully zoomed-out lens and two more rows.

Pros:
>no need for an UWA lens, obviously
>can be used even with UWA lenses, to get even more UWA

Cons:
>parallax problem if there are objects in close foreground (objects may look "cut in half")
>must frame carefully, since most cameras don't have the panorama overlap preview feature
>takes more time than simply using an UWA lens