Ok just to shake things up a little. You can get fairly goods results using vst presets. But unless you understand how these presets are achieved u will never get the exact result your looking for. And for good quality presets you pay good money. like the following....
Waves Signature Series | The Tony Maserati Collection | The Collection
These presets combine many different effects, such as reverb, de-esser's, compressors, chorus, eq adjustment.. etc. etc.
So these are the terms you need to learn to master your. sound. These are all used to add colour, or remove colour from the sound to get it to fit within the mix. Only you know what will blend with the rest of the tracks in your project.
However that being said colouring a scribble just makes it a coloured scribble, adding watercolours to a sketch makes it a piece of art. So never forget your original source material is very important. Read up on microphones, microphone postioning and recording levels, to help achieve this. There are plenty of links in the Newbie section.
In regards to your vocals the best thing to work with is maybe a little reverb, and eq'ing out those frequencies you don't need as to not make your mix muddy.
If you want to use eq's or reverb these will not doubt be already in your software somewhere. So therefore you don't need any free vst's. However if your after a quick fix, that offers presets of famous vocal effects that the stars use, these will cost you money.
Learn more or pay more.