If you've discovered the Evernote widget for notifications center you're on the right track. If you're looking for the next step, download Neato on the iOS app store. This app takes Evernote shortcut's to the next level by allowing you, right in Notification Center, to type a note and add to Evernote. I've been using it all week and it's really amazing.
The Evernote widget is great but it's a shortcut that takes you into the app. If your doing heavy lifting notes or adding photos, reminders or lists - that's the way to go. If you just need to jot something quickly down like a name, phone number or company name, give Neato a shot.
It it also has the capability of posting to Dropbox, Facebook, Twitter etc.
Here's a link to the iTunes store: https://itunes.apple.com/us/app/neato-jot-down-note-save-to/id931243944?mt=8
Available on the iOS App Store