Hey, wanna make music? Yeah? Got a buncha money? No? Well that's perfectly fine, check this free stuff out:
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
As for DAWs, it's been a long while since I've used anything other than FL Studio (not counting Audacity, which I still occasionally use for specific purposes), which, while being the only one I can directly recommend, is paid. However, I've heard good things about Reaper which has a "free trial" that you can technically use forever, akin to WinRAR. Additionally, I've also heard some good things about Waveform Free.
(tags from @secretroomba) Ok saving these tags for later for myself
MORE because there are some additional little things I forgot about:
Geonkick - A drum synthesis VST, especially simple to get kicks going, but capable of producing a multitude of sounds.
plugdata - A visual programming environment for plug-in projects, that people produce their own plug-ins for, such as infamous plug-in the gusher.
SoundThread (info in description) - A really cool node-based audio editing interface based on the Composers Desktop Project, great for sound design, although it currently only supports .wav files.
OpenUtau - An open source software for UTAU voicebanks like Kasane Teto, much easier to work with imo than the original UTAU software for a beginner to vocal synths like UTAU and Vocaloid.
Famitracker - More NES style chiptune stuff, this one's a classic standalone tracker program.
Furnace - Another tracker I've heard fantastic things about from chiptune artists, more fully featured and capable of producing a wider variety of sounds.
I would really suggest looking in the comments and reblogs for additional resources if you would like even more, but I'm coming back some months later for my own personal additions of things that I've played with!:
Tuğrul Akyüz's gumroad page - A multitude of free plug-ins including TugSpect and TugImgSynth which turn the brightness values of lines of pixels in images into unique spectral EQ shapes and wavetables respectively for an interesting form of sound design.
PaulXStretch - A few different people have suggested this one! It's a great, smooth time stretching effect that comes in standalone and plug-in forms, good for ambient textures/soundscapes.
PanCake 2 - A panning modulation effect with easily customizable LFOs (or, panning patterns).
Minimal Formant - A formant shifter (and also tilt EQ), an effect that's kind of like a pitch shifter but for shifting overtones rather than the base tones of a sound, altering the timbre but not the true pitch of the sound.
Youlean Loudness Meter - A plug-in that analyzes sound as it plays and gives you the values of perceived loudness, loudness range, and dynamics. Has a paid pro version but it's not necessary to pay for it. This one has become practically essential to me in mastering my next album for consistent perceived loudness.
PeakEater - A waveshaper/clipping plug-in that's great for gently shaving the top off of some sounds that are too loud without reducing their punchiness.
I'd also like to suggest going on Archive.org for sample CDs and other various things you can find on there. I've gotten some use out of Discovery Firm's Breakbeat Ammo and Zero-G's Jungle Warfare Collection, although be aware of the momentary silence at the beginning of the samples (you can cut that fairly easily but, y'know, just as a heads up).
