The Mac comes with an array of basic software already built in. The Mail and iCal software provide satisfactory e-mail and scheduling, Safari is a good Web browser, and TextEdit performs basic text-editing and word-processing tasks. But you're probably going to want more.

What follows is a list of more than a dozen free or cheap applications to help beef up your Mac. It starts with a few essentials: Applications that virtually every Mac user will find valuable. Then I move on to describe applications that are great for users with specific needs.

Ten of these applications are free, one is donationware, and the other three are priced under $30.

Quicksilver is a powerful toolkit that completely changes the way you find and use information on your Mac and on the Internet. It's a keyboard-based, completely mouseless utility that you use to open applications on your computer, open and work with documents, open URLs in your browser, perform Internet searches, look up words in the Mac's built-in dictionary, and more.

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It's really hard to describe, because there's nothing else quite like it. Application launchers like Launchy on Windows are similar. But Quicksilver is more than just an application launcher.

Here's how it works: You call up Quicksilver by typing Ctrl-Spacebar. A small window pops up in the center of your screen, with two smaller windows inside it. Start typing in the first window. Quicksilver begins to suggest filenames and actions, based on a running index of applications and documents on your system and (with the aid of plug-ins) on your browser bookmarks and history.

Quicksilver also remembers what you type, and anticipates what you want based on what you asked for in the past. An example from my own usage: If I type B, then L, Quicksilver fills in the rest with the URL for the InformationWeek Blog (to which I've assigned the keyword "blog" in my browser bookmarks). Likewise, if I type just the letter N, Quicksilver suggests a file called !next actions which is my running to-do list.

I use Quicksilver every few minutes as I work and play at my computer. The most common things I use it for: Opening applications, opening documents, opening URLs, appending text to text files, and running searches with Google and other search engines. It's completely replaced the Mac desktop and Dock as the place where I launch frequently used applications and documents, and it's replaced the Finder for many functions as well. I often use Quicksilver instead of the mouse to access application menus.

It's an extraordinary program -- and it's free.

Quicksilver is a little tricky to use at first, but Lifehacker has great directions for getting started with Quicksilver.