La Voz Cantante

I'm very impressed with this plugin, soundwise it's by far the best free vocoder I have found and it's actually on par with many paid ones as well. I was searching for a good vocoder VST for a while now and I'm very happy to find that one of the best options out there is actually free. It doesn't have as many options to customize your sound like some other plugins do (e.g. VocalSynth 2), but classic vocoder sounds are very well possible and since you can use your synth of choice as an external carrier signal, you have a wide variety of possibilites anyway.

I also think everyone who likes this vocoder should check out the "Midi Choir" plugin made by the same developer. It simply pitches your voice to the MIDI notes that you play and has a higher polyphony than La Voz Cantante, meaning that you can play chords with more than 3 notes at a time. It sounds really good as well.

If anyone runs into problems, because of the lack of a 64-bit version for this plugin, you should look into jBridger, an application that converts 32-bit plugins to 64-bit.