Here's a list of some free quality VST plugins for common tasks in streaming. These are mostly useful for enhancing your microphone sound and making your voice "fit in" with other audio sources, but sometimes it may also be useful to add processing to sound coming from games or applications.
Keep in mind that they are simply tools - if you don't know how to use them, you might do more damage than good, but if you use them well they can make a big difference.
Compressors and Limiters
- TDR Kotelnikov by Tokyo Dawn Records
just a very well rounded compressor that has all the buttons and does all the things
- Thrillseeker LA by Variety of Sound
Limiter, well suited for pushing the volume on sum signals a bit
- ReaComp by Cockos, from the ReaPlugs suite Just a compressor. Precise, no frills
Equalizers
- TDR Nova by Tokyo Dawn Records
Fully parametric and allows for dynamic equalizing, very indepth and powerful. Can be used as a de-esser
- BootEQ mkII by Variety of Sound
4 Bands semi parametric + an optional saturation stage. Simple & practical for a lot of applications
- TDR VOS SlickEQ by Tokyo Dawn Records
3 Bands semi parametric + a high pass, switchable characteristics. Quick to dial in and totally sufficient for most things
- ReaEQ by Cockos, from the ReaPlugs suite
No frills fully parametric EQ. Will do everything you need.
Gates/Expanders
- Floorfish by digitalfishphones