Open Source Software
One of the best things about open source software (OSS) is that it is free, though that is not its greatest attraction for me. Its that all of the OSS code is developed to be freely available for anyone else to use and develop for their own needs.
Most OSS is developed by communities, with programs like Firefox and Apache getting there strength and usability by the large number of people putting in their ideas to improve and advance the software so that everyone can enjoy the benefits.
Where to get OSSThe greatest repository of OSS is at Sourceforge, which has over 139,000+ projects running and covers an enormous range. Really it is worth a bit of time just to have a bit of a rummage through the software and try out some of the available programs.
Its easy just to Google for free software, but that can lead to all sorts of problems. Poorly developed programs that can crash your computer are common, as well as programs that carry trojans and malware and they can then cause problems both with your computer and possibly financially, with auto-dials being one of the common problems encountered with some "free software".
The safest way of finding and using software is by looking at software that has been used for many years and is current. That along with looking for software that is "community" supported will make your journey so much easier :)