Vital - A powerful wavetable synth, my personal favorite VST synth, very easy to figure out creating new synth sounds, with the help of the plenty of tutorials that are out there for the plug-in. (There are paid versions but they are completely unnecessary to get 99% of the features of the plug-in.)

Synth1 - A classic piece of synthesizer software.

Pendulate - An interesting, chaotic synth that you can make weird little sounds with.

Native Instruments' free plug-ins - Various cool VSTs, including the Komplete Start pack.

The Free Orchestra - A set of orchestral instruments for Kontakt Player (see previous link).

BBC Symphony Orchestra Discover - More orchestral stuff! This one has its own player so you don't have to download a separate VST to use it if you don't want to.

Magical 8bit Plug - A chiptune plug-in, intended for producing sounds like that of 8-bit systems like the NES and Master System.

Genny - A synth VST made to emulate the soundchip of the Sega Genesis/Mega Drive.

MT Power Drum Kit - A nice rock n' roll style drum kit plug-in.

This guy's weird VST collection - 6.4 gigabytes of weird VSTs, including some you might know, like Delay Lama and MeowSynth!

sforzando - A free player for soundfont files.

Musical Artifacts - A resource I mainly use to find soundfonts, on which you can find other various things as well.

Kilohearts Essentials - 30 effect VSTs including reverb, delay, compression, pitch shifting, transient shaping, ring modulation, phase distortion, and more.

Xfer's freeware VSTs - Exactly what it says on the tin, including the one and only OTT compressor.

Illformed - The good ol' dblue Glitch 1.3, Crusher, Stretch, and TapeStop.

Hysteresis and Fracture - Two interesting glitch effects, one being a delay and the other being a buffer.

Codec - A cool digital audio degradation effect.

Le Phonk - A slick distortion plug-in.

MAIM - An effect that mimics the sound of MP3 compression.

Soundly Shape it and Place it - One is simply an equalizer VST, the other is an effect that emulates a speaker (ex: a radio) and a space (ex: a cave).

Fresh Air - An effect that adds high end information to your sounds, to provide brightness.

ValhallaSupermassive - A combo reverb and delay plug-in that sounds quite big.

UnplugRed - A collection of various interesting VSTs, most of which have free versions.

Chowdhury DSP - I can't personally speak for all of these but their tape model effect is great for some lo-fi style effects.

TAL-Chorus-LX - A thick sounding chorus, good for "retro" sounds too.

Polyverse Wider - A great effect for widening sounds up, really simple too with only two controls.

Freesound - A good audio file resource, mainly for foley recordings.

Cymbatics Dubstep Starter Pack - A little sample pack with some good drum and synth samples.

fishmonger drum kit - A pack of samples from the album 'fishmonger' by Underscores!

WangleLine's sample packs - Free samples put out by my awesome mutual WangleLine!

aaand I might as well include this set of drums I made awhile back :P