If you're not already using QuickSilver, stop reading this post right now and download this excellent piece of software. QuickSilver is the quintessential launcher application for Mac OS X and it saves me tons of time.
If I want to launch an application or document I hit the command and space bar keys (which I've mapped to QS) then I enter the first few characters of what I'm looking for, select it from the resulting list (if needed), then hit enter to launch it. All without leaving the keyboard.
Compare the above with using the mouse to dig through Finder windows to find an application or a document. Using the keyboard is infinitely faster and QuickSilver is an application that I can't live without.
If your a QuickSilver novice, practice using it as a launcher for about a week before delving into the following, more advanced topic.
Here's an advanced QuickSilver trick that's a huge time saver if you constantly look things up online - and who doesn't? If you regularly use search platforms like Google, Wikipedia, MacUpdate, IMDB or Gracenote, Quicksilver can save you a bunch of time.
The tip involves using Mac OS X's little-known shared find clipboard to pass text to a search engine while using the keyboard within QuickSilver. For example, say you're reading a blog post in Safari that references a term that you'd like to look up on Wikipedia. Simply highlight the term, hit command-E, then invoke QuickSilver (command-space), type wiki, then return twice. Boom! A new browser tabs opens with your Wikipedia search results. This is much faster than loading up a search engine page and copy and pasting the term into it.
The only problem is that there isn't a QS plug-in for my favorite Web browser (Flock) yet. This means that I can't copy text from a Web page in Flock to the shared find clipboard and pass it directly to QS. I can still invoke QS, type a search engine shortcut (i.e. goog) then hit enter once, then type a search term, but that's a few extra steps. I'm not sure if this is because there isn't a Flock plug-in for QS or because Flock doesn't respect the shared find clipboard's command-E shortcut. If you're a Flockstar, chime in!