The more complex kitchen islands that include a sink and sometimes also a stove with a fume hood.
These islands require more planning. When you already plan to renovate your kitchen and its floor, you might think of providing water, gas and electricity for the island. Once a complex island is done its less flexible, but the advantage is that you face your guests more often during preparing the food and can participate in the communication better. Also you might have more light and space during work then in a classic kitchenette facing the wall.
First, some of my island finds with sinks only:
beautiful country kitchen with blue subway tiles behind the stove and matching stools;
the kitchen island with white marble counter top features two sinks (via Southern Accent)
Italian country kitchen with red counter top and matching stools;
the sink of the island is positioned opposite the stove
although the kitchen already features a sink, the islands provides a second one;
the oven in the back is a pizza oven (!) (via Elle Decor)
nice low budget solution via IKEA
modern kitchen with slim island made in China (via Boloni)
And now, kitchen islands that not only have a sink but also the stove and fume hood:
"English Mood" via Minacciolo
lots of stainless steel and reflecting silvery tiles (via Bofi)
"EL System", industrial look stainless steel solution via Elmar Cucina
chic industrial look via Marie Claire Maison
solution via Ikea for the tighter budget - probably same system like above where the counter top just was larger
You might also be interested in the post Kitchen Islands - Part I - about simple kitchen islands.