Most conspiracy theories online are just the meme-like repetition of posted articles, factoids and pop science obsessions (thermite, for example). Most of those who do the propagation just use copy-paste text to stand up for them. There isn't really a thesis to be proven, just the hunt for obtuse explanations.
Stepping away from familiar turf for amount (ie. diplomatically side stepping 9/11), much of the information comes from clusterfuck blogs and websites such as the (seemingly) far-right
www.rense.com, which leads the internet in NWO-hilarity, chemtrails and holocaust denial.
If you follow any of the biggies:
http://en.wikipedia.org/wiki/Chemtrail_ ... acy_theory
http://en.wikipedia.org/wiki/The_New_Wo ... bertson%29
http://en.wikipedia.org/wiki/David_Icke
http://en.wikipedia.org/wiki/Morgellons_disease
http://en.wikipedia.org/wiki/Homosexual_recruitment
http://en.wikipedia.org/wiki/Jakob_Segal
http://en.wikipedia.org/wiki/Project_Blue_Beam
http://en.wikipedia.org/wiki/Free_energy_suppression
http://en.wikipedia.org/wiki/LaRouche_movement
You can see where they all head back to, profiteering alternative medicine, xenophobia, homophobia, misogyny and fear of sex, antisemetism and lots and lots of pop science swill peddling the same obsessions over and over. Perhaps the greatest dominator is the habit of forming "science" "theories" over frames of footage, photographs and the like. Whether it be looking for the Loch Ness monster in a grainy field, or looking for inward dust clouds on 9/11 footage, the methodology speaks volumes. There isn't a theory, much like the guys looking for Nessy don't know the shape of the animal they're looking for, they're just hunting for anomalies to tag as proof of "something".
Baby Jesus have mercy on my soul for posting in this thread.