Here's a website that gives you an idea of the technique - http://www.decorative-concrete.net/countertops.php
there is also a book on concrete counters that you can buy from amazon.com.
http://www.amazon.com/exec/obidos/tg/detail/-/1561584843/qid=1044562452/sr=8-1/ref=sr_8_1/102-9029442-1597723?v=glance&s=books&n=507846