Open source GIS software or FOSS4G (Free and Open Source Software for Geospatial) has been developed worldwide since 1980s. The first open source GIS software was GRASS which became available for public in the late 1990s - and which is still up and running by the way! Gispo Ltd. actively supports the development and usage of QGIS, PostGIS and GeoServer.
Freedom of charge, compatibility, community and freedom to explore
Open source GIS software are free of charge so you save in lisensing and mandatory administration expenses. Still, the support of development and user community is essential - open source software need developing and administration just like proprietary software. Open source GIS software support countless different formats and global standards (OGC) which makes communication between software easier. If you are afraid to go fully open, you can also pick a hybrid solution where you can use open source together with proprietary software.
Open source GIS software community has hundreds of software development experts from all over the world. Because of the large community software developing is fast and the bugs are found and squished quickly - this improves software security and stability. Open source GIS software also have the trait of you putting your own hands into the dough - you can develop, edit, copy and share the open source software yourself! The user has the freedom to choose the open source software and the provider separately which frees the user from tecnhology and provider dependencies.
QGIS is an easy and versatile open source GIS software (desktop) for processing and analyzing GIS data. You can use QGIS regardless of your operating system and it supports a wide scale of formats in your hard drive or database. QGIS has a vast set of different tools including a bucket full of editing tools. QGIS is an unparalleled open source GIS software for basic and advanced users - and it's free of charge of course!
Everyone probably knows PostgreSQL - PostGIS is an extension for PostgreSQL which gives it the intelligence to understand spatial data. PostGIS enables the interoperability of the database and geometries. You can save, analyze and process GIS data with hundreds of PostgreSQL-functions. You can process a quite extensive data and optimaze GIS solutions for your organisation. Here's the last tip: PostGIS works quite well with QGIS through DB Manager extension.
GeoServer is an open source GIS server by which you can share, process, edit and visualize GIS data. Using and administrating GeoServer is quite easy because it is done directly in web browser. With GeoServer you can read and create GIS interfaces that follow the standards (OGC). You can use WMS, WFS, WCS, WMS-T and WPS sharing protocolls with GeoServer. You can add data to your onlinemap in real time as well as publish your maps.