Before you down vote, bare with me as I'm a developer! I've always been curious how designers render their work onto a phone to show their customers how it may look on the phone, for example:
(Source: Dribble)
I'm assuming that's exactly what they're doing, using some kind of 3D rendering of an iPhone and transforming their image to fit the screen. Any tutorials would be great... just satisfying my curiosity, thanks.
Search around for "mockup template". There are some free ones out there, and some paid. These allow you to easily create a realistic mockup using whatever artwork you desire.
Here's one good resource: http://www.pixeden.com/psd-mock-up-templates
Related question: How can I take an iPad psd file and put an image inside it?.
I've usually used this tool for this very purpose : http://placeit.breezi.com/.
You can make images like this in adobe photoshop. Open your image and then put your screenshot of website inside the device. Take a look at this tutorial http://blog.appdemostore.com/2014/10/how-to-add-your-screenshot-to-phone.html.
Or you can use some tool like placeit.net, picapp.net, magicmockups.com.
Placeit.net has many images with different backgrounds and you can download a small image for free or a big image for $8 or $28.
Picapp.net has also many images but without background. The images are .png and you can choose a simple device or a device in hand. The price is $5.
Magicmockups.com has not so many images, but you can download them for free (or you can donate if you want). All images are with background.
