Virtual Economy Manipulation!
Gaia Marketplace Notifier was a simple "market intelligence" app for Gaia Online. Rather than fully breaking the website's ToS and creating an automated marketplace bot, this program was written to give you a notification if an under-priced item was listed on the marketplace, allowing you to buy it manually (remember, no ToS breaks!) and re-sell it for a profit.
It was driven with JSoup, a Java HTML parser that could use DOM, CSS, and JQuery-like methods for extraction of data from a page. It simply monitored a page that showed the most recent marketplace listings and would compare that item's average traded price against the price of the new listing. If the listing was cheaper than the average price, the program would notify you, telling you the item name, how much (potential) profit you could make, and providing a link to the listing.
This program was last tested for functionality in June, 2015. I have no plans of updating the code since I don't use Gaia Online anymore, and if someone else wants to use the code, it should be fairly trivial to update.
Many of these projects were done for fun and out of a love for programming. They may not be polished or even complete. If you'd like more information about a given project or the process used in creating it, you can always contact me.