"Elle Apparel: crib bedding/bumper tutorial"--I've heard mixed things about whether you should even use a bumper in a crib, but just in case I do use one (and feel like customizing it) here's a great tutorial to keep in mind~
DIY Crib Sheet: Sew easy! This blog also has tutorials for bumper pads and a crib skirt! Easy to follow instructions. This will probably be the tutorial I use (if I can get my act together and make my own crib bedding).