I like CMD + CTRL + D while hover your cursor over any word in a Cocoa app. This brings up the dictionary entry for that word. You can also access the Thesaurus this way and click "More..." to get the full Dictionary app to load.
Very useful when reading long academic papers outside of my field.
If you hold Cmd+Ctl after that, you can mouse over other words and the panel will follow.
Also, for those that like the panel but can't always remember the shortcut, in the Dictionary app's preferences you can set the "Look Up in Dictionary" context menu item to open as a panel instead of opening the app.
Having a system-wide Dictionary is something I would not have thought anywhere as valuable as it has turned out to be.
I use this all the time. Incidentally, if you open up the Dictionary app itself, you have access to complete Wikipedia as well. I really like the way Apple formats Wikipedia's pages... they're much cleaner than Wikipedia.org. And yes, the pages are current... it's just that Dictionary app uses a different CSS sheet.
My favorites are the emacs-style shortcuts that work in all native textfields is OSX:
ctrl+f - move one character forward
ctrl+v - move one character backwards
ctrl+n - next line
ctrl+p - previous line
ctrl+k - delete to the end of the line
ctrl+d - delete the next character
ctrl+h - delete the previous character (backspace)
ctrl+o - insert a newline below the current
Using the ctrl key takes some getting used to if you've used a Mac for a long time (I mapped mine to caps lock in the system preferences) but once you learn these keys they are incredibly useful.
As an emacs user, two problems with these key combos that are constantly burning me:
When I hit ^A in a text field of my webmail app (Fastmail) it reloads the page I'm typing in, losing all the text I've entered so far. You have no idea how hard it is for an emacs user to stop doing this. So be very careful on web pages.
I keep using kill-and-yank subconsciously because I'm trained in it. But the kill ring (is it even a ring?) gets preserved... idiosyncratically in Mac OS X, particularly when you move from app to app, and of course it is completely separate from the clipboard where copies and pastes go. I quite commonly kill something and then can't get it to yank, or kill something and then try to paste it and fail.
Actually, I find C-w more annoying in web browsers. In emacs, I have it bound to backward-kill-word, and use it almost as much as backspace.
In firefox, the results are not too good. The tab dies, taking the entire textbox with it. Annoying.
The moral of the story is to not use software other than emacs. I use Gnus for mail and w3m for light web browsing, eliminating any problem with keybinding emulation. It is emacs, so it acts like emacs.
For heavier web browsing, I use conkeror. It is almost like emacs, but not quite. Better than anything else, though.
Sure, try moving cursor to some line in TextEdit (with a document that is large enough to have scroll bars), then press ^L — the line with cursor becomes centered.
I find it amusing that OS X has the best GNU-style keybinding support of any of the major OSes. I tried using emacs-style keybindings in Gtk+, but it just doesn't work as well as Apple's implementation.
That's OK, though, because I don't leave emacs very often ;)
Thanks everyone! I wrote the original article. Not only have I learned a bunch of new ones (the floating dictionary is sweet) but I've discovered ycombinator too! Thank goodness for pingback, eh?
Wow... that's even faster than Skitch! I've been using Skitch (http://www.skitch.com) for over a year now and has saved me a ton of time. I'll give GrabUp a try!
Very useful when reading long academic papers outside of my field.