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.
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).
Fugu SSH is a Mac OS X graphical frontend to OpenSSH's Secure File Transfer application (SFTP). SFTP is similar to FTP, but, unlike FTP, the entire session is encrypted, meaning no passwords are sent in cleartext form, and it is thus much less vulnerable to third-party interception. Fugu allows you to take advantage of SFTP's security without having to sacrifice the ease of use found in a GUI. Fugu also includes support for SCP files transfers, and the ability to create secure tunnels through SSH.