You could draw your own post-it graphic by following a photoshop tutorial . . . 

. . . Or you could generate a post-it note using a free web site set up for the purpose.

If you’re technical but are short on design skills, you can use any of the many template sites on the internet to buy or download a design layout template ready for use. Most of the templates available to purchase are not what I am generally looking for. I want clean CSS designs with good graphics that I can use to

• improve my own CSS skills
• alter for my own purposes easily

There is a wonderful Croatian site call Solucija featuring free CSS templates – which are also excellent. I use these frequently and I normally end up with designs that are quite different from the ones I started with. But you don’t have to do it my way. Take a look.