Free flexible open source todo manager featuring hierarchical tasks
Task Coach - Your friendly task manager. Task Coach is a free open source todo manager. It grew out of frustration about other programs not handling composite tasks well. In addition to flexible composite tasks, Task Coach has grown to include prerequisites, prioritizing, effort tracking, category tags, budgets, notes, and many other features. However, users are not forced to use all these features; Task Coach can be as simple or complex as you need it to be. Task Coach is available for Windows, Mac OS X, and GNU/Linux; and there is a companion iOS app.
An open source Mac OSX RSS reader with support for RSS/Atom feeds
Vienna is an open source Mac OSX RSS reader with support for RSS/Atom feeds, article storage and management via a SQLite database, written in Objective-C and Cocoa. Feeds can be accessed directly, or through a syncing service supporting the Open Reader API, like BazQux.com, FeedHQ.org, InoReader.com or TheOldReader.com. Development now happens on GitHub: https://github.com/ViennaRSS/vienna-rss
Smultron is a text editor written in Cocoa for Mac OS X Leopard 10.5 which is designed to be both easy to use and powerful.
Monolingual is a program for removing unnecessary language resources from Mac OS X.
A multi-protocol instant messaging app for Mac OS X
Adium is an Open Source, multi-protocol instant messaging application for Mac OS X. Adium supports AIM, ICQ, Jabber, MSN, Yahoo!, Google Talk, Bonjour, Gadu-Gadu, Novell Groupwise, SIP/SIMPLE (Text), and Lotus Sametime. Additionally, it supports all of these applications at once so, even if you have multiple IM accounts, you don't have to log into each account separately.
PDFView is a simple, yet powerful, Mac Os X PDF viewer, with advanced integration with LaTeX.
Stop-motion movie production software for OS X. FrameByFrame enables you to create QuickTime movies from pictures taken with any camera/webcam connected to your Mac, including built-in iSight cameras.
A feature-full Cocoa FTP client for OS X. Support for advanced queuing, bookmarks, quick connect, and drag and drop.
iTheater is an open source project that aims to create a media center application for Mac OS X, to fully take advantage of Apple's OSX. The project aims to integrate most media-based Mac applications into a single console (or media center).