Well, Perdido Street Station, The Scar and Iron Council are all set in the world of Bas-Lag, and can be seen as loosely structured series - the events in TS follow from PSS, but focus on a different set of people in a different setting, while IC takes us back to PSS' setting and does carry on some of the same themes.
His only 'standalone' to date is of course King Rat, and his first collection, Looking For Jake is yet to be released (I Think), so I guess the poll is a trifle premature!
