I'd recommend reading these essays of Paul Graham's if you want to write more clearly:
http://www.paulgraham.com/writing44.html
http://www.paulgraham.com/essay.html
http://www.paulgraham.com/philosophy.html

I think Paul Graham's style is exactly right for communicating with a broad internet audience, so I'd recommend reading as much to copy his style as to absorb the content.  He thinks really clearly and that clear thinking comes through in his writing.

This series of Less Wrong posts is also a good read:
http://lesswrong.com/lw/ke/illusion_of_transparency_why_no_one_understands/
http://lesswrong.com/lw/kh/explainers_shoot_high_aim_low/
http://lesswrong.com/lw/ki/double_illusion_of_transparency/

To write better you might try the following vague formula:
* Find an idea that you think your reader already understands and is an important prerequisite of what you are trying to say.  Or describe a particular case study from the world.  (Eliezer Yudkowsky recommends opening with a case study: http://lesswrong.com/lw/bc3/sotw_be_specific/)
* If it was an idea: Write a simple one-sentence summary of the idea, identifying it by whatever term is commonly used for it.  Include a link somewhere in the sentence for readers who *aren't* already familiar with the idea.
* In the next sentence, make some kind of straightforward extension of the idea or case study.  For example, connect it to some other idea, identify a flaw, extract a general principle, etc.  Make it so these sentences are totally comprehensible and stand on their own.
* Keep doing that until you've gotten where you need to go.
* Repeat from the first step if you need to introduce a new idea/case study.
* Connect all these threads.  Figure out how the ideas add up, contrast, etc.
* Read your essay aloud repeatedly until it comes across as smooth, conversational, and fluid.

It might be useful to adopt a kind of formal logic approach: explicitly state a set of premises, derivations, and conclusions.  For example, try to structure your thinking using syllogisms: https://en.wikipedia.org/wiki/Syllogism  Syllogisms aren't for proving things so much as giving the reader a map of the argument--a scaffold for its internal structure.  And the premises of a syllogism can, in turn, be other arguments with their own internal structure.

In general it makes sense to lean hard on related concepts your reader may already be familiar with.  Be as simple as possible but no simpler.