Backup files and folders using FBackup, a Free file and folder backup tool.
Backup your folders using SyncBack a Free file backup tool (sync tool not reviewed here)
Easeus Todo File Backup:
Backup your files using Free backup tool Easeus Todo File Backup a Free file backup tool.
Create an encypted area to store your folders and files with free encryption tool True Crypt
A basic tutorial of how to use the tools in Free image/photo editing tool Paint.Net
(Only available for Windows operating systems)
Desktop e-mail client:
Bring your Hotmail and/or your Yahoo Email right to your desktop using Thunderbird
Libre Office: Calc
Libre Office: Calc - Learn how to use a Free alternative to Microsoft Excel.
Diagramming and Charting Tool:
Libre Office: Draw
Libre Office: Draw - A free alternative to Microsoft Visio, can export your diagram to filetypes of BMP, GIF, JPEG, PNG, TIFF, and WMF
Stellarium - Free Planetarium Software