If you are running a CBO campaign, you can add columns which show daily and lifetime budget remaining.
These add the total to the top of the column, under the header.
To turn these on, first go to the Data menu and pick "Campaign":
Then click Metrics to open the Customize Data panel:
Open the Settings section and select the check boxes to turn on these columns:
Finally click the Apply button in the upper right of the configuration panel, and these columns will be added to the report page.
Tip: You can click and drag the column header to move it to a different position.