Years back I was a regular subscriber to Computer Music](ComputerMusicMagazine). They had a [Cover DVD that contained samples, video masterclasses and, of course, a bundle of free Vsts.
Synthesisers
Vital Surge XT Odin 2 Full Bucket Zebra CM
Eq
Compression
Modulation
Delay
Reverb
Effects
ReaperJS
These obviously require Reaper](/aw/music/daw/reaper), but, once you have Reaper (and I love Reaper), there are a truckload of JSFX plugins, written in a language called EEL which allows you to write a plugin in a few lines, and see and hear the results immediately. Often, if you know exactly what you are after, you can write a simple specialised [JSFX plugin to do exactly that task and nothing much else, compared to a Vst author who has to guess what the myriad users might want.