I’ve been using Dash as one of my code snippet managers (along with Gist for public snippets & Coda). I originally chose Dash for its shortcut auto-fill features (and it’s free with in-app upgrade on the Mac App Store!), but have recently found its offline documentation completely excellent.
I primarily use the WordPress and PHP docs, but some others have come in handy too. I like to take my laptop down to the café to work and I’m not always connected to the net when I work down there, so the offline docs are amazing at those times.
I also recently discovered that Gary Jones has published Genesis 2.0 docs, which I’ve found really useful.
As it happens, you can create Dash docsets from HTML files, so I have done that with Gary’s Genesis docs. Offline Genesis reference! Sweet!