Disk Diag allows you to quickly scan your hard drive and check for files that can be deleted to free up space, a very useful tool for Macbook Airs or older Macs with limited space. While it doesn't offer more advanced tools for cleaning up hard drives, the interface is very clean, and you can find everything you need in just a couple of minutes rather than waiting for a 30+ minute scan.
After installing Disk Diag, which goes directly to your Applications Folder and can be accessed from Launchpad, you must select your Home folder. Once done, you can run scans anytime and they will run in just a couple of seconds. Keep in mind that the app has its own definitions of what can be deleted so always check the list it provides of old files you don't need. The list includes Download folders, browser data, mail downloads, and other files that some people like to keep. You can turn them off at any time with the click a button. When set, hit "Delete" and it will wipe the files. It's a great looking app, the interface is very intuitive, and the resulting free space will help your computer run faster if you're always short.
If you need to clear up space on your hard drive fast, are tired of stumbling from task to task deleting things you actually care about, and don't want to dig through the unnecessarily complex OS X disk utility tools, consider downloading this free app from the App Store.