I use a bunch of VSTs, so I thought I should share the wealth (of information) so others can check them out. All of these are FREE.
Simulanalog guitar suite:
JCM900, tubescreamer, DS-1, SD-1, Oberheim PS-1, Univox Univibe, Fender Twin
They all sound good, but I only use the tubescreamer and the JCM900, which sound fantastic.http://www.simulanalog.org/guitarsuite.htm
A lot of people like the Lecto, which is a mesa/boogie VST. I like the Legion, which is an incredible high gain amp with a great tone. He's got plenty of amps on here, all sound great, and also the LeCab, which is a very good speaker cab simulator that uses very little CPU power. The LeCab 2 is even better, but uses more CPU and you have to get impulses for it. I use both cab sims, they're great. Also has some Mac versions.http://lepouplugins.blogspot.com
And since you need impulses for LeCab 2, here's a shitton of free ones! Also known as "god's cab" impulses.http://signalsaudio.com/index.php?optio ... &Itemid=15
Dirthead: A mesa-boogie clone, basically. Unlike others though, this one actually sounds like a mesa. The tone knobs are very sensitive, so I advise moving them just a fraction at a time. Also, when you use it there's a little glitch; whenever you load a project file, you have to re-click the channel selection LED on the amp. When it loads, no channel is selected, and each iteration of it uses like 70% of your CPU, so it's pretty nasty. I get around that by leaving it bypassed before I save and close any project files that I'm using it on. When I open the song up, I just un-bypass it, and everything's fine. That small glitch aside, it sounds fantastic. It has a built in cab simulator that's okay, but I don't personally like it. I use the LeCab 2, and the combination is great.http://www.ndzeit.org/guitar/dirthead.html
Acme Bar Gig - Shred 1.0
A good product, high quality sounds, etc. They have a marshall clone that can do metal sounds, but overall it's more suited to hard rock and less. I've used it on a stoner metal/bluesy hard rock song of mine successfully. Still a great product, and free! http://www.acmebargig.com/product/shred/
Also by the same company is the Razor:http://www.acmebargig.com/product/razor/
The series 60, which they say is their heaviest amphttp://www.acmebargig.com/product/series-60/
and the C-15http://www.acmebargig.com/product/c-15/
They have a lot more, search under "products"
Aradaz amp VST. I use a ton of VSTs, I've probably tried every free one out there, and honestly I don't remember how good this one is. It's still on my computer though, so it can't be bad. Anyways, it's free and there's also Mac versions.http://aradaz.blogspot.com/p/download.html
They also have a nice cabinet simulator that has 5 or 6 different cabs and allows you to use any combination of them. It sounds really nice.http://aradaz.blogspot.com/search/label ... 0Simulator
Nick Crow Lab. His 7170 is a 5150 clone, and the 8505 is a 6505 clone. Both sound incredibly good. His tubedriver is a tube preamp, but I've never used it. I probably should try it, as his other stuff is top quality.http://nickcrowlab.blogspot.com
Also, the simple combo. 3 knobs, very metal, and perfect for those with limited CPUs, as it uses very little.http://requietus.blogspot.com/2008/11/n ... o-gui.html
The wagner sharp MKII. I haven't tried this one yet, but I will today. I'm sure it will sound great.http://requietus.blogspot.com/2008/11/n ... i-gui.html
Wurr Audio Green Machine. It's a nice amp sim that pretty much does everything. It has a ton of options, and a ton of gain, and really captures the "marshall roar" kind of sound. It's really a nice sounding VST. This VST really can do about any amp sound you can think of. I've had an issue with it freezing up/crashing sometimes when I use it in Reaper. Still worth looking into though. Also on this page are a tube booster and reverb.http://www.greenmachine.pwuq.de/Wurr_Au ... nload.html
Ignite amps. The NRR-1 was apparently made for the guitarist of Fleshgod Apocalypse. I haven't tried it yet, but I plan on it. Also has mac versions.http://www.igniteamps.com/index.php?opt ... 55&lang=en
Bluecat freeware pack. It's a pack of various tools, spectrum analyzer, EQ, gain controller, flanger, chorus, and all very high quality.http://www.bluecataudio.com/Products/Bu ... ewarePack/
I've tried more, but I didn't think they were good enough to post here.
I'll try to record some quick samples of many of these and post them here over the next day or so.