Note: This question is specifically about installed, desktop software. There is another question specifically about free cloud-based software and services.
What free programs should every GIS user have installed?
I'm not necessarily referring to ESRI extensions or open-source products, but others that increase your productivity and ability to handle GIS tasks.
- Notepad++ for writing code snippets or editing XMLs. Paint.NET or GIMP for quick graphic editing.
- I use Google Tasks daily and I think it's worth mentioning. It's not GIS-specific, but it's a great tool, especially if used independently and on multiple projects where purchasing time-management software isn't reasonable.
- While it's not focused on GIS development, Rainmeter has proven to be very useful in terms of increasing productivity and monitoring system resources. I have created a GIS "sidebar" on my desktop that holds all of my development tools, as well as links to the online resources I used the most. It's nice to be able to use one location, rather than many (e.g. taskbar, bookmarks in browser, search engine).