For the past few years I have been using Quicksilver for OS X, an application which has dramatically changed the way many people get things done on their Mac. Here are a few things you can do fairly easily (if you want to be as cool as me).
With the Quicksilver web search plugin, all you need to do to use Google (or any other site with a search form) is activate Quicksilver (my shortcut is ctrl-space), start typing "google" until it shows up, press tab-tab, type your search, and press return. Check out the video below to see what I mean.
Here I am searching google for "weather 12180", and then getting a map from Troy to the Albany airport.
Bookmarks with Firefox 3.5
To get Quicksilver to index your bookmarks in newer versions of Firefox, you have to change a Firefox setting so it creates legacy bookmark data upon quit. Here's how.
To use Twitter from Quicksilver, I activate Quicksilver and press period to enter text entry mode, type my tweet, press tab and start typing "tweet" until it shows up as an option, then press return. This sends the message to twitter, which updates my Facebook via the Twitter application for Facebook. The script also updates my iChat status, and gives me a Growl notification of the success. Yes, this one makes me feel super cool.
To set this up, you must add an "Action" to Quicksilver. An action is just an Applescript located in ~/Library/Application Support/Quicksilver/Actions. In this case, it is this file, called "tweet.scpt":
iTunes Fade Out and Pause
This is my favorite. If you know me, you know I am obsessive about my music collection. I refuse to store anything that is not Lossless, etc. On my Mac, if iTunes is playing, and I press ctrl-alt-cmd-space, iTunes will fade out slowly, then pause. When these commands are pressed again, iTunes will resume playing, and slowly fade in.
This is done using a Quicksilver "trigger". A trigger can be assigned to any keystroke, and can potentially perform any action. In this case, it is running an Applescript, which can be found below.
Anyone who uses a Mac and would like to be able to accomplish things a bit faster should install Quicksilver. It is free. I do not think there will be anymore official updates to Quicksilver, as the person who developed it is now working on the Google quick search box. You can still download beta updates for Quicksilver here. Last time I checked, the Google QSB did not have advanced features such as triggers, and was merely an application launcher/web search interface.