http://www.quilt.com/FAQS/SashikoFAQ.html
http://www.secretsof.com/content/1569
The above sites give you a little history on sashiko. It's basically a form of embroidery using a running stitch. Sylvia Pippen has some gorgeous designs.
http://www.sylviapippendesigns.com/patterns.html
If you google Sashiko you will find lots and lots of information and many patterns. Have fun!