Complex widget form UI – examples and best practices

I’m contemplating a widget with quite a number of options, which will make for a lengthy widget form. To improve the user experience with this form, I’d like to divide it into sections. I don’t feel like re-inventing the wheel, so what are some examples of widgets that have fairly complex forms (especially those which are divided into multiple sections) all the while remaining usable and easy to parse visually?

I should add that I’m looking for examples that could be considered “best practices”, not messy kitchen sink forms that are difficult to use. I realize this is probably subjective.

Thanks for your input!

How about native Thickbox with the native jQuery tabs for example:

the widget it self is simple and only has a link

but one you click on it the thickbox pops up and shows all of the options grouped by tabs:

let me know what you think I’ll fetch the code for you.