I'm actually writing this post using the Evernote app. What I love about new media and technology is how it can simplify your workflow. I've used my phone to email myself a quick note about a story idea. Nothing crazy, just a sentence or two while I'm waiting in line or whatever (I hate waiting, I'm impatient).
I always write what exactly the note is for so I'm not completely lost when I get to it at a later date.
i.e.) This sounds like a cool name: Jadzia (Yes, I like Star Trek) or
Possible title: Invading the Shell (actual title of a short story of mine)
I've been an Evernote user for awhile now an it's been a great way to organize and manage individual projects. Not just for writing but also for design gigs.
Another app I use is called the My Writing Nook which is synced with an email account. This is the one I use when I'm in between classes and have nothing but time to kill. I've purhased a portable weather proof keyboard that can be rolled up and stuffed in my back pack for longer entries (tapping the screen can be tiresome).
So these are two of my favorite simple writing apps. If you have any that you use, feel free to share your experience with it here.
Simple apps I use for writing: