I've gathered 170.000 spam messages by intercepting all spam reactions on ByteMods.com. It has been running for four years now, gathering IPs, the actual content and whether it would actually pass the captcha if it wasn't intercepted. Below are some of the analysis I've done on that spam and its content.
TL;DR 45% of spam messages beat the captcha. Of all countries, Bangladesh sends the most spam about viagra (by far). China has the most spambots. Russia excels in spamming about actual spam.
TL;DR ish On average, january received the most spam (new years resolution?) and july the least. Valium was a huge trend in 2012.
Created by Tim Quax
Spambots per country
Amount of spam originating from country
Spams about spam, per origin spambot
% of spam per country that's about viagra
Spam trends
Viagra Insurance Valium Misc. drugs