Whereas time sheeting records resource effort - ideally with charge out rates and internal costs as appropriate - budgeting and expense management potentially includes all of the project costings - both forecast and actual.
In general software should provide functionality for budgeting and tracking of all expenses, and reporting these through some kind of appropriate dashboard.
This is an area where we are already aware that mashups might be very appropriate - there are great timesheet applications out there - can we provide direct integration that works between a timsheet solution and a project management functionality set?