It's weird, after years of WSYWIG fontabulous editing software plaintext as a format seems to be making a bit of a resurgance. It's a great way to hold information, hard to muck up and super easy to share.
But plaintext is plain and that's a problem. It's good to have some sort of context and structure in your notes along with tools to manipulate that structure.
But there's a few good tools out there to help you make semantically rich information in the plainest of plain formats. Markdown is great, as is Taskpaper and actually HTML kind of falls into that category too.
What the hell am I talking about? :)
Mostly the excellent work of Jesse Grosjean and in particular the recent upgrade release of Folding Text. What does it do? That's really hard to explain so check out the site and click on video at the bottom.
Not for everyone but definitely worth a try and luckily you can get a time limited trial by clicking right here
Thanks to Shahid Ahmed for proselytising FT :)