This is a list of, in my opinion, the best guitar simulators - whether they are free or not. I have split the list into two sections: Free and Non-Free. I have added a brief description of each one, as well as a link to the product`s web-page.
Free modelers
There are many free guitar simulators that are just as good as commercial ones. You should definitely check them out. Huge credit to the individuals who created them! Note: many of these are JUST pre-amp simulators which means you need some sort of cabinet simulator after them in order to sound good. I recommend impulses - a guide on them is coming very soon.
SoloC
A great simulator modeled after the legendary Solando SL100 head. It provides amazing tone anywhere from crunchy sounds to heavier lead tones.
Creator: LePou
Link: http://lepouplugins.blogspot.com/2009/03/soloc-v11.html
HyBrit
Another great amp created by LePou. Possibly my favourite amp sim for that sweet classic rock sound. Great cleans and crunch tones. It also comes with a fullstack version (cabinet simulator included)
Creator: LePou
Link: http://lepouplugins.blogspot.com/2009/08/hybrit-series.html
Le 465
LePou`s new amp, based on the raging Engl E 645 Powerball. It`s most useful for created thick, heavy, hi-gain tones. If you want some brutal metal or engaging hard rock tone, this amp is for you!
Creator: LePou
Link: http://lepouplugins.blogspot.com/2009/10/le456.html
AcmeBarGIG
This is actually the name of a developer, not an amp sim. These guys have releases so many amazing amps, that I decided to just put it all in one. Just take a look at their website. Every one of their plug-ins are quality!
Creator: AcmeBarGIG
Link: http://www.acmebargig.com/
8505
A very brutal sounding simulator. Based on the extremely-heavy 5150, this amp will blow your speakers due to it`s insane levels of gain and brutality!
Creator: Nick Crow
Link: http://nickcrowlab.blogspot.com/2009/05/nick-crow-8505-lead-tube-guitar-amp-vst.html
AradazAmp Crunch
Just like the title says, another great sounding crunch amp!
Creator: Aradaz
Download link: http://ariearadaz.googlepages.com/AradazAmp_Crunch_v1.4GUIA.zip
Developer website(check it out for more GREAT amp sims as well as quality plug ins): http://ariearadaz.googlepages.com/AradazAmp_Crunch_v1.4GUIA.zip
Non-Free section coming up...