OilCan is a native Universal Binary multithreaded query tool for PostgreSQL. It supports multiple query windows and multiple queries in one window, and includes a basic schema browser. Each query window gets its own connection. All queries run in their own thread, allowing other operations to continue while a long running query is running.
TwistedWave is a very easy-to-use and powerful audio editor. It supports Audio Unit plug-ins and many file formats, including wav, aiff, caf, mp3, mp4, FLAC, and Ogg Vorbis. It has good multichannel support, so you can apply Audio Units to a selection of channels. It supports unlimited undo and redo, which work instantly. Zooming in and moving around the waveform is very fast, even with very large files. All the effects are applied in the background, saving a lot of time.
OsiriX is an image processing software dedicated to DICOM images produced by medical equipment (such as MRI, CT, PET, and PET-CT) and confocal microscopy (LSM and BioRAD-PIC format). It can also read many other file formats: TIFF, JPEG, PDF, AVI, MPEG, and Quicktime. OsiriX is able to receive images transferred by DICOM communication protocol from any PACS or medical imaging modality. OsiriX has been specifically designed for navigation and visualization of multimodality and multidimensional images.
Address Book Server allows you to share your contacts and calendar events with others connected to your network or over the Internet. Each participant synchronizes their contacts with the server hosted on your own system. Address Book Server supports the full Address Book and iCal schema. The server also provides a friendly Web interface and an iPhone client which let you access your contact details remotely.
Bean is a rich text editor with many niceties added to make writing convenient, efficient, and comfortable. It is, to use a horrible cliché, Text Edit on steroids. It uses Apple's NSText object to do most of what it does, but adds live word count, the ability to adjust printed margins, and lots of other bells and whistles.
Phage is a two-player abstract strategy game. It is somewhat similar to chess, in that each player has different-looking pieces that move in different ways. A game of Phage is finite: there is a fixed upper limit on the moves that can be performed, so games are usually quite short.
NSFileHandleExt is an Objective-C extension (Cocoa/GNUstep) for the NSFileHandle class (which handles files/sockets). This extension provides support for much easier network programming for protocols like HTTP, IRC, telnet, etc. (everything that sends messages in lines suffixed by \n).
SmartMines is a minesweeper game for Mac OS X (Tiger and above) with a few features that make it stand out when compared with many other minesweeper games. For instance, it features "smart clicks" that make it easy to both mark and uncover with single button mice. Also the minefield window is resizable, so actually hitting the square you want will not be the greatest challenge.