Really, this could be a single-app channel, because Evernote is the best. Yup, we said it... And the more you use it, the more useful it becomes. If you're not into Evernote, try it: Becomes seriously addictive after a while.
A pretty pricey notepad which strives to actually work as a journal. You can put photos into your notes, which can be nice. Don't buy it before you try Evernote first (which also lets you embed photos into notes).
This used to be huge, and then Automattic (the company behind Wordpress) bought the service. Still useful, though, especially if you don't want to sync to Dropbox (Simplenote is its own cloud service).