Since I had to reinstall my MacBook Pro after an SSD Drive fail, I stumbled upon a list I made, containing software essentials and basic application that everyone needs when reinstalling the OS. I compiled an up to date list: which applications are the essential apps in 2011/2012 when reinstalling Mac OS X.
This handy little app is a free un-packer, replacing Archive Utility that comes with Mac OSX. The Uninstaller does not only support .sit and .zip files, but also .rar, .7z and many other archive formats. This app is essential when working with archives and downloads.
A replacement for Quicktime and also for VLC. It has a nicer interface than VLC and supports the same file types (codecs) that quicktime does not: .h264, DivX, XVid, MVK, etc. mPlayerX recently became my favorite Media Player.
An awesome Mail.app replacement with great interface and actually improving the mail reading-experience: Sparrow has many features, such as perfect GMail integration, multiple accounts, avatar syncing from facebook, and many more. Recommended!
The best To-Do application out there. Best of all: Wunderlist is not only free, but it also synchronizes automatically via the web and your ToDo-Lists are available via web-interface as well as on any operating system (iOs, Android, Windows, etc.)
Best way to keep your Mac de-cluttered at all times: Clean My Mac from MacPaw deletes cache files as well as leftovers (junk from previously installed apps, etc.), Language files and so on. A perfect tool to keep the OS snappy at all times.
VoodooPad (former VoodooPad Pro) is an awesome offline desktop Wiki. I am using VoodooPad to store and interlink my ideas, texts and written content. It can hold RTF data: text as well as files from your hard disk can be directly linked. Images can be embedded or referenced. Highly recommended!
Apple Xcode is a free download via the appstore. It is not only needed for creating iOS and Mac OS Applications, but also to compile unix applications and to get other developer applications, such as Quartz Composer installed on your system.