Synergy is Free and Open Source Software that lets you easily share your mouse and keyboard between multiple computers, where each computer has it's own display. No special hardware is required, all you need is a local area network. Synergy is supported on Windows, Mac OS X and Linux.

The Dropbox powered social network

DomainBrain is a handy tool for Mac OS X that helps webmasters and web designers keep track of server and login information for websites they maintain.

Everyday git interface for human beings.

Loremify is a one-click tool to copy Lorem Ipsum. It lets you wrap in html, specify the amount of text, and copy it to your clipboard—all in one click. It runs as a Dashboard Widget in Mac OS X, and is a mere 400kb download.

Stellarium is a free open source planetarium for your computer. It shows a realistic sky in 3D, just like what you see with the naked eye, binoculars or a telescope.
It is being used in planetarium projectors. Just set your coordinates and go.

As the only integrated solution for encryption and backup, Knox 1.6.4 makes securing your files easier than ever. Create as many encrypted vaults as you want, each with separate passwords. Then schedule automatic backups. You can even reformat USB sticks and external drives as encrypted Knox vaults — moving files between Macs has never been so simple and secure.

Vanilla is an open-source, standards-compliant, multi-lingual, theme-able, pluggable discussion forum for the web.

Adobe® Digital Editions software offers an engaging way to view and manage eBooks and other digital publications.

A really nice Delicious bookmarks manager for the mac

At fontcapture.com you can create a font from your very own handwriting. There's no software to download and install, all you need is a printer and a scanner.

Unity is a multiplatform game development tool, designed from the start to ease creation. A fully integrated professional application, Unity just happens to contain the most powerful engine this side of a million dollars.

Atmail is a Linux based Webmail Client + Email solution. Use as an alternative to Gmail or Exchange, and bring your organizations email under control.

Software claims to convert any psd to a WordPress theme. The proof will be in the pudding.

iTool is a free multifunction utility for a complete system maintenance and cleaning. It’s even easer to use now with the new version 2, especially for the “first time” users. It’s new GUI will help you choose quickly the needed task.

An Open Source RubyCocoa Gmail Notifier for Mac OS X

What do people use to get the job done?

You're running out of disk space? You want to clean your hard disk to free up some space and get rid of the clutter? Sponge is a tool to keep your Mac clean and tidy. With Sponge you can reclaim your disk space by removing applications, finding duplicates and tracking down large files.

Isolator is a small menu bar application that helps you concentrate. When you're working on a document, and don't want to be distracted, turn on Isolator. It will cover up your desktop and all the icons on it, as well as the windows of all your other applications, so you can concentrate on the task in hand.

A Social Browser for Mac OS X Leopard

REAPER is reasonably priced Windows software for multitrack audio production.

Check Off is a to-do list that sits in your Mac's menu bar. Simply click the check mark and your personal to-do list will drop down.

I've played with the Bento beta preview and I really liked it. It's basically a desktop database that is easy digestible and highly customizable which is the best part about this application.

Our idea is to be a simple, user friendly, beautiful desktop for normal people.

Dockables provides you with one-click system event access right from the Dock in OS X.

boastMachine is an open source, state of the art publishing platform that makes your web publishing experience so fun and easy as never before! From the fully automated installation to advanced content management featuresto spam fighting, boastMachine pro

Paint.NET is image and photo manipulation software designed to be used on computers that run Windows. It supports layers, unlimited undo, special effects, and a wide variety of useful and powerful tools.

A simple (and free!) Ruby on Rails weblog application.