Use your Mac long enough and it gets bloated with unwanted files, caches, and incompletely installed apps. I've got three free tools for you that will clean out your Mac, and along the way boost your productivity as well.
This is the single best all-around Mac cleaner you'll find, and it's free. (If you want support, you can also pay for it.) It cleans out a wide variety of system caches, as well as caches and other files from applications including your browsers and many popular programs including Adobe Reader, Adobe Flash Player, Microsoft Office, and others. It's got an uninstaller as well. And it will also repair your Mac's permissions, although it's somewhat controversial whether that does anything for your Mac. Still, this is a great program for cleaning your Mac.
This freebie performs some similar tasks to CCleaner, but does more as well. It empties system, user, Internet, and Font caches, can fix problems with Spotlight and Mail indexes by rebuilding them, lets you configure hidden parameters in Finder, Dock, QuickTime, Safari, Mail, iTunes, login window, Spotlight, and many Apple applications, and does more as well.
Deleting apps on a Mac seems simple -- just drag it from the Applications folder to the Trash icon. And it's true, that is simple. Unfortunately, though, some apps leave a lot of junk behind, and just dragging the app that way won't clean them out. There's a solution: Download the free AppTrap. It cleans out the junk, not just the app.