At the most expensive, but perhaps the most polished, end of the spectrum is Intuit's QuickBase. Intuit has a reputation for quality online services and QuickBase delivers. It can only import files in CSV and not from Excel formats directly. This is a real database application, and the default operation is to take each row of your spreadsheet and turn it into an individual record. You have lots of controls over reports, and, as we mentioned, tons of templates.
If you want to import your Excel files directly and don't want to pay a lot of money, then start with Smartsheet. They have a nice mix of features and reports, and seem to work in a variety of Web browsers without trouble. If that service doesn't have a rich enough feature set for you, or you want to have more collaborators, then consider TrackVia or QuickBase if you can afford the monthly fees. I would steer clear of the others for the time being.