I’ll answer with preventative thoughts first:
If you use Firefox, set your master password. That’ll require them to enter the master password before they can log in to any site. It’ll also require them to enter the master password before seeing your saved passwords.
Did you know that in Firefox, you can go to Options->Security->Saved Passwords and see all of the saved passwords right there, in plain text? You can! In Chrome, you can go Options->Personal->Show saved passwords and see those in plain text too! Surprisingly, Internet Explorer doesn’t save like those two do. In Opera you can go Preferences->Forms->Password Manager to see the account names, but not the passwords.
To the best of my knowledge, nobody has snooped on my PC. I’ve always been one to lock my computer when I leave it. And that uses a unique 10-digit password that includes special characters, numbers, and upper+lower case letters, and is a non-dictionary word. So it’s certainly safe from somebody just sitting at my keyboard taking guesses, given that there are ~94^10 possibilities.
For my web browsing, I use Chrome. I have all of my passwords and website stored. But I keep no shortcut to it on my desktop, taskbar, or start menu. Instead what you’ll find is Opera shortcuts. I’ve got unimportant data saved in Opera, as a bit of a decoy in case anyone does care to snoop around.
My coveted adult film collection sits in C:\Porn. I’m not afraid of people finding those videos.
The only thing I really worry about is people finding my Fluther account. It’s been my hidden treasure for over a year. I’ve said things I wouldn’t say if I knew people from RL would see it.