I use Todoist for anything with a deadline or intended end date, and Google Keep for my notes 'n stuff. Wunderlist is also great for lists.
How's Google Keep? Is it easy to organize with? I used an early version a few years ago and I didn't take to it. But I'm open to trying again. I use simplenote (nvALT on my mac desktop) and it's too basic. A scrolling list down the lefthand side of the program without a good way to organize further.
They added a bunch of features since then. You can now change the color of notes, add labels to them or 'sticky' them, which means they'll stay at the top. It's also possible to draw now in the app. You can also insta-keep web pages with the browser plugin. It can also use pictures, so you can just snap a picture of whatever you want to remember or keep. And you can switch between having checkbox or not. All features that I don't use regularly, but they're there when I need them and make it a good tool to use for me.