I use colored pencils. So long as I use a light mark I haven't had any trouble getting them out. I also use washable graphite. For dark fabrics, Clover makes a fine line white pen. It takes a few minutes to develop, but the mark doesn't come off until the quilt is washed.
Magic chalk is popular with my friend who long arms - it also comes off with washing or ironing.
Lots of quilters use the blue marking pens. I haven't been able to bring myself to use them yet.