I think my best ux story was from around 2004. The company I worked for only sold through sales reps, so when people came to view our products, they had to contact a sales rep to purchase. Support was getting a ton of phone calls because people could not figure out how to contact a sales rep and we had a high bounce rate on product pages.
I did some "basic" research and developed a flash (back when flash was considered cool) widget for the product pages that allowed users to look up a sales rep right there, without reloading the page, based on their zip code. It then stored that rep info in a cookie so whenever they went to another product page or came back to the page in the future it displayed the rep right there for them to contact.
From what I understood, measurable sales increases were in the 100 million range according to market lead generation. (was a 1.5 billion/ year company)
** Cant believe it, but the page im talking about is actually archived on way back machine! **
Yikes.. my designs back then.. =/ lol