I've been waiting a long time for a mobile spreadsheet application that can do more than just create basic data tables. Apple's Numbers app for the iPad fits that bill.
If you aren't already familiar with the Numbers app, hop over to Apple.com and take a look at their description. Features like check boxes, steppers, sliders, and pop-up menus in addition to the impressive charts makes Numbers quite a powerful tool.
The Numbers app comes with only a very small number of templates, and because it is such a vastly different tool from Excel, not many Excel templates can be directly imported into Numbers without a loss of data or functionality.
Update 3/1/2018: You can download a few Numbers Templates from Vertex42.com for free. We aren't creating any more new templates for Numbers, though, because the Excel app on iPhone and iPad works extremely well. Most of the spreadsheet templates available from Vertex42.com have been updated to work in the Excel app.