I use tiddlywiki, a single file javascript app accessed with a browser and stored in dropbox (tiddlywiki.com). Supports some version of markdown, and importantl

I use tiddlywiki, a single file javascript app accessed with a browser and stored in dropbox (tiddlywiki.com). Supports some version of markdown, and importantly for me, has many plugins including one for Latex. I think the search and tagging features are what make it awesome.