Is there any free or cheap apps that can view/edit MS Excel files that are located on Dropbox? For my iPad I use CloudOn, but I have nothing for the iPhone. The reason I'm looking for free or cheap is I really only use it to manage my book list. I keep track of what I've read and what I own in an Excel workbook with multiple sheets. Just doesn't feel right spending $10 for just that. I appreciate any suggestions.