I tend to obsess a bit about creating an optimal work environment for myself. This blog post focuses on the software setup that I have that works for me, focusing on the little glue utilities that are so helpful. So I won't cover the big local apps (email, browsers, productivity, test/dev) or web apps (todos, photos), that's for a future post.
Witch ($14, Many Tricks) - Maybe the one I use the most. I find that the default OS X cmd-tab switching to be annoying by cycling through apps instead of windows. Maybe that's just because I spent so many years living in windows and this mimics the Windows behavior, I don't know, but this is what I consider natural.
iTerm 2 (free) - Replacement for built in terminal.app. Terminal isn't bad, but the one feature this has which I miss from old terminal programs is auto copy selection contents when switching to another app. I do that all the time. Doesn't just save a few keystrokes -- seems every time I expect my selection to be in the clipboard, and when it's not, I find myself hunting around.
Hyperdock ($10) - Another one that takes the best from Windows, in this case two nice features of Windows 7. This one feels a little overpriced.
-- Snap window. If you drag a window up against the top border, maximizes. Drag to aside, maximizes to fill up that half of the screen
-- Window preview. Basically Aero peek. Show a little preview of the window when hovering on the dock icon. This is a nice-to-have-frankly.
Growl (free) - the best way to get async notifications from other apps. Only question is why isn't something like this already built in?
Fluid (free) - I like web apps I use a lot (gmail, Remember the Milk, google calendar) to function like real apps: own icon, startup and quit behavior distinct from other browser windows, etc. I've now come to appreciate those as Site Specific Browsers (SSB's), and Fluid is the best way of doing those. It's a little strange as that relies on Safari, and I use Chrome for everything else, so those SSB's don's share cookies or anything else, but that's not a big deal. Fluid even has some nice little special cases, like adding unread mail badges to your gmail icon (neat!)
Alfred (free, for now) - successor to QuickSilver, but still lacking a bunch of features, like plugins. Jury's still out for me on this one, I find I'm using spotlight more than alfred still. But of this class of sites it seems to be the best.
Homebrew (free) - command line app package manager. My current package list is:
atk git jasper mysql unrar
autojump git-extras jpeg nmap watch
cdargs glib libgcrypt pango wget
dialog gnupg libgpg-error pcre wireshark
dos2unix gnutls libtasn1 pkg-config xmlstarlet
figlet gtk+ libtiff readline
gettext iperf mtr unix2dos