Day six: Had to hunt for the Library folder
After my application house-cleaning, I realized today that I probably left a bunch of orphaned files in my Library folder since I just tossed apps the other day. When I went to look for the Library folder, I discovered Apple has hidden it. It's still there and there are plenty of ways to get to it – the easiest to me is click the Finder's Go menu and press the Option key (you can use "chflags nohidden ~/Library/" in the Terminal to permanently make it visible as well).
This isn't a huge issue since most of us rarely visit this folder, but it's definitely worth noting.
As I suspected, I'd left preferences files and application support files behind. Didn't add too much when I cleaned that out though.
Note: if you're not comfortable cleaning out the Library folder, you can also use a tool like App Zapper when removing old apps.