Not sure about freebie stuff. Most of the free stuff I got came with Cubase and I rarely use em cause once you buy some decent plug-ins, the free stuff sounds like crap.
If you want a good package, go with Pluggo. There's a ton of stuff for a decent price.
Other than that, I'd recommend BBE Sonic Maximizer for vocals and acoustic guitar. PSP VintageWarmer for compression, Spectral Design Voice Generator/Voice Processor for vocals, TC|Native Reverb Master, PSP84, Spektral•Delay, Karlette (echo), Antares Auto Tune, MicMod (mic emulator), Grugelizer (for that old radio sound), Magneto (for warmth), MDA De-ess.
And finally, t-Racks for mixdown.

The ones that get the most use are the TC|Native Reverb Master, PSP VintageWarmer, Karlette and t-Racks.