Do you feel you're in a rut with your productions?   Struggling to create new sounds?   Or simply on the lookout to expand your synthesized horizons?
Well here are the synthesix - 6 different methods of synthesizing sounds...

1. Additive
By giving complete control over every harmonic or partial in the sound, additive is one of the most versatile, but also difficult synthesis methods to get to grips with. However, it's a simple concept - reconstructing complex sounds out of really simple ones.   A collection of sine waves all played at different frequencies to create the sound. 
Generally, additive synths will give control over just a few groups of partials, just to simplify things, so it's a little more user-friendly. 

2. Subtractive
Far less computationally expensive than additive and very commonly used, subtractive synthesis begins with an oscillator that generates a waveform such as a sawtooth or square wave, then uses filters and the like to remove harmonics from the tone, altering it - kind of like when you say "ahhh" and slowly close your mouth until it becomes an "oooh" (if you can resist actually doing that now, you have an inconceivably strong will!)

3. FM
Frequency Modulation or FM synthesis is a fast-track to interesting and obscure tones.   Perhaps this is why they are so popular with Dubstep producers, who frequently employ FM synthesis to make increasingly more disgusting bass synths.
This is done by frequency modulating a waveform (when the amplitude stays the same, but the frequency is modulated) with another waveform.    This distorts the tone and gives all kinds of unexpected and fun sounds! 
If you modulate a wave with another wave that's frequency isn't an integer multiple of the original wave (I'll give you a moment to wrap your head around that one, it took me a while) then you can get dissonant and even percussive sounds from it!

4. PM
Phase Modulation or PM is what you get when some Japanese synth manufacturers decide to prove just how smart they are.   While the rest of the world's computers were struggling under the strain of subtractive synthesis, Casio's researchers let their processors have a holiday with PM.
PM simply processed the samples of each wave at a varying speed.   By reading out the first part of the wave really fast, then holding the loudest point of each high and low point of the wave for longer than normal, it created a really interesting tone with a tiny computational cost.
The most brilliant part however (and much simpler to understand as well) comes when you add in the second wave in the PM synth.   For example - if you have a square wave in slot 1 and a saw wave in slot 2, it would play a square followed by a saw over and over again in quick succession, making a completely new tone. 
These are great for making unusual resonant tones.

5. Granular
A close relative of sampling, Granular synthesis involves cutting samples up into really tiny segments of only a few milliseconds long called "grains", then playing them back at different speeds, phases, volumes and pitches to create all kinds of intriguing timbres!
You'll probably know the sound as the one from the film The Matrix, where neo has the silver goo going down his throat after taking the red pill. 
It's great for that time-stretchy sound and more for ambient soundscapes and effects than lead synths or basses.

6. Wavetable
Wavetable synths are basically modified additive synths.   They have tables of different waves made up from additive synthesis, saving the user from having to make each individual wave. 
Then, they allow the producer to play back the waves looped in quick succession, also allowing them to determine how far through the wave the loop should begin, resulting in some very unusual harmonic sounds!