OK, I've never posted these elsewhere, but as it's R.T.. here's my absolute-dogs-danglies free VST toolbox I turn to time and time again. Note these are all COMPLETELY free to use - not that I'm (much of) a skinflint, but I'd rather find something free that does the job well than pay for something that does it almost as well.
VST Instruments* Sub Freak ->
http://www.delamancha.co.uk/subfreak.htm. Take this, put it through a compressor, and you have some SERIOUSLY heavy sub bass for your track.
* Itchy Synths ->
http://www.dubstepforum.com/free-synths ... 90924.html. You can probably guess from the link, but somebody over on dubstep forum released a load of free VSTs, and god damn they kick ass. I'll admit I usually turn to paid-for synths for instruments such as Massive, Sylenth, and I'm debating whether to buy Razor (I probably will), but these are definately worth looking at, and insane quality for free.
* Valsier ->
http://audio.betterthanclay.co.uk. Some people may recognise the name Cube:Hard in the hardcore scene. Well, he made a synth, and it's REALLY good. Great for growly basslines.
* ReFX Beast ->
http://www.kvraudio.com/get/242.html. An oldie but a goodie. Kind of like a synth vs acid machine hybrid. The Atari presets and Hard 303 are great. This is how I got that seriously heavy bassline acid line in the Raving Windows remix Paul liked
VST Effects* Betabugs ->
http://www.betabugsaudio.com/plugs.php. A great selection of really useful FX. Check out widebug in particular.
* TAL-Dub II and TAL-DUb III ->
http://kunz.corrupt.ch/products/tal-dub - really good reverb effects, perfect for jungley stuff.
* LIvecut ->
http://mdsp.smartelectronix.com/livecut. Great for autochopping of breaks and other samples. Comes with a "normal", "squarepusher", and "warp" preset

* Glitch ->
http://illformed.org/plugins/glitch. Everyone knows about this, so don't use it too obviously or people will just say "oh, they've used Glitch, meh". Use it sporadically and I can't remember the name, but use the last fx unit to the right to get that timestretch effect you used to get on old jungle tracks, such as "whattt's the ttiiiimmmee docccotttoorrr dreeeddd". POW!!
* EQ Killer ->
http://free-plugin-list.com/plugin.php?id=201. Sometimes you just want a very simple hi/mid/low EQ kill/fade plugin like you have on a mixer. This will do it for ya

Hope that helps
