They do really well in deep shade (but will tolerate some sune too.) The flowers are small, purple and on little stalks, but the leaves are the stars of the show.
I wasn't a fan originally, but now that I've learned how many beautiful varieties there are, I'm a convert. They do well in pots or in the ground and are easy to grow from seed.
AND you can take cuttings at the end of the season, root them in water all winter and plant them out again in the Spring (well after last frost). Free plants forever without seed saving--not a bad deal!
Google image search shows the amazing variety: http://www.google.com/search?q=coleus+deep+shade&hl=en&prmd=imvns&source=lnms&tbm=isch&ei=nhajT4WlEubx6QHDn7km&sa=X&oi=mode_link&ct=mode&cd=2&ved=0CCsQ_AUoAQ&biw=1024&bih=428#hl=en&tbm=isch&sa=1&q=coleus+varieties&oq=coleus+varieties&aq=f&aqi=g2g-m1g-mS2&aql=&gs_l=img.3..0l2j0i5j0i5i24l2.279015.282359.0.283375.9.9.0.0.0.0.875.1922.2-1j0j2j0j1.4.0...0.0.JNsoSDOTOPY&bav=on.2,or.r_gc.r_pw.r_qf.,cf.osb&fp=d5eb415ac89ecd6e&biw=1024&bih=428