Provides extra options for aggregating data in tables - e.g. grouping sets of rows together and summing the values of particular fields.
Has a hook - hook_views_aggregation_functions_info() - which lets you add your own options to the table aggregation settings - e.g. supposing you have a limit for something (number of tickets, nights of accommodation) and want to decrement it - you can write a method to sum the matching rows and then do a calculation on the total.
Also supports 'add column function' - adds a grand total (or other summary field) at the very bottom of the table.
Caution - this module breaks hook_views_pre_render() - you can write your own pre_render method to remove or shuffle entire rows, but any chances to values will be overwritten (discovered this by looking through the source and looking for the use of that hook). The workaround is to try and do what you need to by using hook_views_aggregation_functions_info() instead.