Best Open Source Win
LibreOffice is a free and open-source office suite that is compatible with other major office suites, and is available on all operating systems. It is an independently-developed version of the OpenOffice.org suite.
The office suite includes:
LibreOffice - Writer, a word processor with similar functionality and file support to Microsoft Word . It has extensive WYSIWYG word processing capabilities, but can also be used as a basic text editor.
LibreOffice - Calc , a spreadsheet program, similar to Microsoft Excel . It has a number of unique features, including a system which automatically defines series of graphs, based on information available to the user.
LibreOffice - Draw , a vector graphics editor and diagramming tool similar to Microsoft Office Visio . It provides connectors between shapes, which are available in a range of line styles and facilitate building drawings such as flowcharts. It also includes features similar to desktop publishing software such as Scribus and Microsoft Publisher .
Sumatra PDF is a free PDF, eBook (ePub, Mobi), XPS, DjVu, CHM, Comic Book (CBZ and CBR) viewer for Windows.
Sumatra PDF is powerful, small, portable and starts up very fast.
Simplicity of the user interface has a high priority.
7-Zip is a file archiver with a high compression ratio.
The main features of 7-Zip
High compression ratio in 7z format with LZMA and LZMA2 compression Supported formats: Packing / unpacking: 7z, XZ, BZIP2, GZIP, TAR, ZIP and WIM Unpacking only: AR, ARJ, CAB, CHM, CPIO, CramFS, DMG, EXT, FAT, GPT, HFS, IHEX, ISO, LZH, LZMA, MBR, MSI, NSIS, NTFS, QCOW2, RAR, RPM, SquashFS, UDF, UEFI, VDI, VHD, VMDK, WIM, XAR and Z. For ZIP and GZIP formats, 7-Zip provides a compression ratio that is 2-10 % better than the ratio provided by PKZip and WinZip Strong AES-256 encryption in 7z and ZIP formats Self-extracting capability for 7z format Integration with Windows Shell Powerful File Manager Powerful command line version Plugin for FAR Manager Localizations for 87 languages
7-Zip works in Windows 10 / 8 / 7 / Vista / XP / 2012 / 2008 / 2003 / 2000 / NT. There is a port of the command line version to Linux/Unix and macOS.
VLC is a free and open source cross-platform multimedia player and framework that plays most multimedia files as well as DVDs, Audio CDs, VCDs, and various streaming protocols.
Simple, fast and powerful media player. Plays everything: Files, Discs, Webcams, Devices and Streams.
Plays most codecs with no codec packs needed: MPEG-2, DivX, H.264, MKV, WebM, WMV, MP3...
Fast and compact image viewer/converter trying to be simple for beginners and powerful for professionals. Many supported file formats and features. Features included: multi-language support, Thumbnail option, Painting, slideshow, toolbar skins, fast directory browsing, batch conversion/editing, multipage editing, alignment (rotation) of single pdf pages around a small corner (e.g., 2 °), scanning to pdf-Files, OCR_KADMOS plugin, file search, change color depth, scanning, cut/crop, IPTC edit, capturing, lossless JPG operations, effects, ICC support, EXE/SCR creating, many hotkeys, command line options and plugins.
GIMP is a freely distributed program for such tasks as photo retouching, image composition and image authoring. It can be used as a simple paint program, an expert quality photo retouching program, an online batch processing system, a mass production image renderer, an image format converter, and more.
KeePass is a free open source password manager, which helps you to manage your passwords in a secure way. You can put all your passwords in one database, which is locked with one master key or a key file. So you only have to remember one single master password or select the key file to unlock the whole database. The databases are encrypted using the best and most secure encryption algorithms currently known (AES and Twofish).
Inkscape is an Open Source vector graphics editor, with capabilities similar to Illustrator, CorelDraw, or Xara X, using the W3C standard Scalable Vector Graphics (SVG) file format.
It supports many advanced SVG features (markers, clones, alpha blending, etc.) and great care is taken in designing a streamlined interface. It is very easy to edit nodes, perform complex path operations, trace bitmaps and much more. We also aim to maintain a thriving user and developer community by using open, community-oriented development.
Audacity is free, open source software for recording and editing sounds. You can use Audacity to record live audio, convert tapes and records, edit sound files, change the speed or pitch of a recording and much more.
InfraRecorder is a free CD/DVD burning solution for Microsoft Windows. It offers a wide range of powerful features; all through an easy to use application interface and Windows Explorer integration.
A free and open source web browser descended from the Mozilla Application Suite. Firefox is highly extensible, with thousands of third-party add-ons available.
Firefox version 60+ (Quantum) is presently faster than Google Chrome and use less memory than Chrome. Compare to previous versions of Firefox, the Quantum version is twice as fast, promote parallelism, and has more intuitive user interface.
Thunderbird is a free, open source, cross-platform e-mail, news and instant messaging client. The project strategy is modeled after Mozilla Firefox.
It supports POP (storing mail locally on your hard drive so that it can be accessed without an internet connection), and IMAP. It features excellent mail filter capabilities and management.
Thunderbird has strong support for using multiple accounts and identities, including automated signature features.
Chat functionality is built in, so you can enjoy real-time conversation with your contacts, right from your favorite messaging application, with multiple supported networks. Thunderbird makes it easy to search through both past conversations and received emails.
Thunderbird can also function as an RSS/Atom feed reader, and has a large selection of add-ons that extend it with calendar support, PGP support, integration with online services and much more.
Available also as portable app: http://portableapps.com/apps/internet/thunderbird_portable
Thunderbird for Android is known as K-9 Mail