A tutorial with Todd Oldham and Susan Sarandon on how to use plastic cups and fabric paint to create a modern circle pattern on your sheets. You can also check out the how to instructions in the book Todd came out with a while ago called Handmade Modern which is filled with great MCM inspired DIY ideas.
Make it Mine Magazine shows us how to make a potato stamp using a cookie cutter (for those of us less confident with our freehand abilities).
For regular potato stamping instructions, check out poopscape's tutorial on how to make the lemon slice pattern above. Or if you're not into making your own stamps, there are plenty of etsy crafters who can make them for you. Check out Bossom Stamps to start.