You can set any size for a sidebar (read more about sizes). Sidebars can be specified, for the whole site, for each category or page type, or individually for each page / post. You can create as many sidebar as you wish. There are 6 different layouts to use:

[columns] [column width=”1/3″]

Right sidebar

[/column] [column width=”1/3″]

Left sidebar

[/column] [column width=”1/3″]

2 sidebars

[/column] [column width=”1/3″]

2 right sidebars

[/column] [column width=”1/3″]

2 left sidebars

[/column] [column width=”1/3″]

No sidebars

[/column] [/columns]