Microsoft Corporation, the creator of the Office software suite, offers free online videos and tutorials for Excel 2013 via the Office support website. The tutorials range from the basic functions needed to operate the program to advanced functions that can assist even well-versed users of Excel.
GCFlearnfree.org also provides step-by-step resources for various tasks in Excel, which are provided via online manuals as opposed to videos. Practice workbooks are available for download by the user, which assist in practicing the functions being learned in real time to better assist in the learning process. GCFlearnfree.org provides basic and advanced tutorials as well, including a quiz to enable the user to see how much of the material was retained.