Pretty low-fi: mostly Dropbox.
- Core language notes are kept in per-language files (eg.
js-notes.js).
- Useful snippets of JS and CSS are in test files. The ones done by conscientious past self have notes on which browsers I tested at the time, most don't ;)
- Bash config is sourced from Dropbox; and a couple of Sublime snippets are backed up manually.
I also share a few things in Bitbucket Snippets, although it's not my primary system - just a way to share.