The default sticky notes app for OS X is great, but you can't use it for any type of confidential information you might want to keep at the ready. Memo is a simple stickers application that let you store your notes with password. It also claims to sync with iCloud, and lets you separate which memos to sync and which not to. You can set you memos to autolock after one minute or lock them manually. You can also set one password for each individual note. You can download it freely in the Mac App Store.