Evernote is becoming indispensable for me. You can make text and audio notes, take photos, then save them grouped by category with tags. It’ll sync to the desktop app. Both are free (although a $5 a month plan allows you more storage and other features.) There are getting to be a multitude of third-party add-ons, always a sign an application has achieved critical mass. It’ll search text within snapshots too, like within a business card.
A companion app Fastever, allows you to new a new note quickly.