Here are some things you might see: addresses of friends and family members, letters and cards from friends, business cards of doctors and hairstylists and other professionals, a few inspirational quotes... and a weird handwritten list.
It looks something like this:
dork
geek
nerd
loser
jerk
idiot
fool
doofus
butthead
And you'd probably raise an eyebrow (if you can raise only one eyebrow, which I can't) and make an excuse to leave.

But wait, I can explain! I'm a writer!
See, when I first started writing for children after completing two adult novels, the insults on the tip of my tongue weren't kid friendly, so I had to find some cleaner alternatives. Since my main character was going to be an eleven-year-old boy (a demographic I know quite well from working in elementary schools), I knew this kid wasn't exactly going to call his friends "silly" or "funny." No. Boys this age are quick to make fun of each other. So I did some research.
Now that I'm pretty firmly planted in the middle grade genre (for now), I need that list handy on my bulletin board. Because kids -- real and fictional -- are mean... and sometimes funny. (My personal favorites are geek and nerd, because I am both.)
What kinds of things in your life might seem strange to someone, especially someone who isn't a writer, but you could explain away by saying, "I'm a writer!" Do you collect something? Keep a list or log of anything? Find pictures of people who look like your characters and save them on your hard drive? (Guilty...) Do share!