A few resources for PSD mock-ups that you may find helpful if your a designer or an illustrator or a marketeer.
I have used this in the past and their is nothing wrong with saving time by finding great assets pre-built ). But it costs $10 a month and frankly, after a few months of downloading it tends to not be worth it to continue the membership. Great for interactive elements, flat design interactive elements, icons and more.
I am new to this website and service, and in general am quite pleased with the fact the majority of this material is free and well put together. Not quite as useful in the same ways Pixeden is with interactive mock-ups, but its great for posters and print work.
Mobile/Tablet Previews Only. Huge free resource, a lot of this stuff you can find elsewhere but its all nicely collected here.
Book covers, can covers, any type of print cover you can think of it’s here. The quality isn’t great but for simple mock-up purposes this site has resources that can suffice. One negative draw back is some of these are action scripted items that are not built as PSDs but rather simple scripts that are prepared for you to build your own assets in PSD format. I Guess this is cheaper than hosting zip files of PSDs but its a pain in the ass to wait for an asset. Definitely a site meant for someone who’s got patience.