Most Mac OS X users appreciate the simplicity of Mac application installation; it usually involves nothing more than a drag and drop out of a disk image, or simply unzipping a download. Still, some apps, plug-ins and other digital goodies require an installer, which means you're entering your password and granting permission for a program to place files anywhere on your machine.
If you've ever been curious (or concerned) about this operation, Apple's default Installer app (found in /Applications/Utilities/ and used by most independent software vendors - but not all - use to distribute their products) can display a log of every file a piece of software installed on your machine, accessible under File > Show Files after the Installer finishes its work (but before you quit/close it, of course). As you can see, the log is even searchable, making it easy to sift through those big install operations.
If you want to grab a copy of this log you can of course select all the text and copy/paste to your own file, but most installers (including those not from Apple) should place a copy of the install log in ~/Library/Logs, in which case you can use the Console app (also in the Utilities folder) to browse through those logs and easily mail a copy (with help from this tip) to a friend or developer. Some installers, however, place the log directly on your Desktop or on the root of your hard drive, and in my experience, most of those don't put a copy in the default logs location at all. Tsk, Tsk, guys.
These tools should make a handy addition to your tool belt if you're beginning to keep a more watchful eye on what gets put where by these installers, or of course if you're simply interested in learning more about how Mac OS X is built and where files go to get the job done.