User Manager is a supplement to the "Accounts" pane in the Mac OS X System Preferences, designed for use with small home networks. User Manager is targeted at power users who desire full control over user and group attributes, without the need to resort to using the NetInfo Manager. With it, you can create, edit, or delete users and groups in any Open Directory node (e.g. a NetInfo domain). The interface allows you to edit nearly all record attributes, including UID, GID, login shell, and home directory. You can also manage Unix group memberships using the drag-and-drop user and group-centric interfaces.
SpotLook is a graphical interface to Mac OS X Leopard's Spotlight desktop search engine. It features tracks, which are timelines showing results according to their date. Tracks can created, edited, and customized, and include a search scope and attributes to search for. Found items can be viewed with Quick Look or revealed in the Finder.
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.
SynthTest is a somewhat simple application for OS X that allows you to pick a MIDI source, a MusicDevice AudioUnit, and an Effect or MusicEffect AudioUnit to play with. You can open an edit window for both the synth and effect. If they do not have a custom edit GUI, the generic editor view will be used. SynthTest has a reference implementation of preset support for Audio Units. It is primarily intended to be used by Audio Unit developers for testing purposes (the source is available), although it can be great fun to play with all by itself. It is complete enough to be used for live performances.