Yep, I sewed some suede elbow patches onto an old cardigan last night. Good times.
I mostly followed these simple little instructions. You could use any material you want, but suede or suede-like fabrics are easiest because you don't have to worry about frayed edges or trying to fold under a hem around an oval-shaped patch. That can be a freakin' pain. It helps if your Mom recently gave you a LARGE bag of leather scraps to play with. Otherwise, I'm sure you can find something suitable by rummaging through the remnant bins at JoAnns or cutting up some Coach/Louis Vuitton/Prada bag. Though I would ask the owner first.
(Oh hey, shout to Sister on her birthday!)