Way back when the OS CMS's weren't given the benefit of enterprise doubt, one had to select from proprietary vendors: Vignette, Sharepoint, Adobe Contribute, etc. We chose Sharepoint, but I hope one day they'll hire a Drupal intern :) But I'm grateful to have honed some ASP.NET and Active Directory chops at this internship.
A simple database-driven one-pager which allows the Adidas boys to track any discrepancies with their online product listings. Working with Adidas was a treat, they're fun folks!
An online travel guide, similar to Fodors and Lonely Planet. BJ had a massive repository of travel reviews & articles written by colleagues, which he published using Drupal. Development for this site included extensive integration into mash-up APIs (google this, yahoo that), as well as some fancy Flash & AMFPHP (ala Services).
My claim to fame -- I got to write in-house applications for Adidas! This was a simple one-page app that mapped Adidas representatives to their respective Universities. Just a convenience to their in-house guys.
Replaced Bigfix's original homegrown CRM solution with Drupal & CiviCRM. Now this was a big project. It included migrating all of their old data (pre-Migrate), custom Flash development, and more.
The site was a one-stop to fill out all forms needed for legal processing of Felony expungements. I created FillPDF for this site, which merges PDF templates with CCK or Webform data. Some Java web services on Tomcat stuff.
Unfortunately, the guys saw the worst of the economy misfortunes and had to close shop :(
This site was built by the good folks at ChapterThree, I'm just one of the current maintainers. Learning some good performance tactics (memcached, APC, etc). Will be upgrading the site to Drupal 7 using Moshe's Migrate strategy.
The "OpenID for Charities". One place for charities to upload their information, one place for donors to budget their donations. An API for 3rd parties to escrow donations from other sources.