CleanMyMac X - Clean, protect and speed up your Mac
YoutubeMultiDownloader - Just like its name YouTube Multi Downloader, it is an online website for downloading the videos of downloading without using any video download and accelerator.
DaisyDisk - DaisyDisk is a disk analyzer tool for OS X that visualizes hard disk usage and allows to free up hard disk space.
KeepVid - A free web application that allows you to download videos
Fossils - Find and clean out all your old unused files
ShareTube - Watch YouTube, synced with friends.