The best programs and add-ins for Microsoft Office Excel.
Daniel's XL Toolbox
Daniel's XL Toolbox is a free collection of open source tools that allow you to analyze and present data contained within the Excel sheets. It includes functions to move or extend graph ranges, apply watermarks, save and restore graphs, and draw graphs for publications. It allows you to analyze data with correlations, regressions, multiple histograms and much more. Once installed, all new tools become accessible from the Excel toolbar (all versions). Download from here.
As its name clearly suggests, Excel Accelerator is a free toolset that allows you to speed up the most common operations in Excel and integrate the functions of the famous Microsoft program with new features very useful. It allows you to perform complex calculations and extends the functionalities related to texts, duplicates, formulas, calculations and much more. Once installed, it must be selected from the Excel settings menu (all versions) and it appears in the toolbar. Download from here.
Excel Mixer Nano
It is a program for Excel free thanks to which you can adjust and vary the values present in the Excel cells with simple scroll bars and observe the reactions of the formulas and graphs of the program and the changes made. There is also a paid version that allows you to export graphics as images, export data as text files, perform advanced analysis in two clicks and much more. Download from here.
Compatibility Pack for Office 2007
The name doesn't lie. It is a compatibility package released by the same Microsoft which allows you to open files in the new XML formats generated with Office 2007 and later also in Office 2003. This means that, by installing it, it is possible open Office 2007/2010 XLSX files in Office 2003 without having to buy a new version of the program or having to make tedious conversions. Download from here.
It is an add-in for Microsoft Office Excel from version 2007 onwards that allows you to encrypt your spreadsheets using an external file as a security key. It allows the user to choose the encryption technique and customize all the properties related to data protection. It supports encryption from 601 to 3001 and runs in VBA for Excel. Not very easy to use at first glance but very useful. Download from here.
From version 2007, Microsoft drastically changed the user interface of Office introducing the tabbed toolbar system Ribbon. Although several years have passed since then, there are still many users who are not comfortable with this type of UI and UbitMenu comes to meet the latter restoring the classic menus of the old Office in Office 2007/2010. Just install it and the old classic menu appears in the menu tab of the Ribbon interface. Download from here.