Simplenote is an easy way to keep notes, lists, ideas, and more. More info »
It has now markdown with extra formatting!
It has unofficial android apps (Jadenotes, and there are others)
Very fast and very sleek. Does nothing but store your notes in plain text + supports tags. I love it, both the online application and the iPhone app. Ad-supported (but in settings it says Display Ads: Off ???).
