GNUSTEP Live CD contains a lot of software for GNUstep, a free implementation of the OPENSTEP framework (which is also directly used in Mac OS X as Cocoa). It includes excellent applications for RAD (GORM and ProjectCenter). The CD is available for i486, AMD64, Apple Mac PowerPC, and Sun UltraSPARC computers.
IP*Works! is a comprehensive suite of more than 40 native Linux class libraries for Internet development. It is a robust framework of enterprise-class tools, enabling rapid integration of any major Internet protocol or technology, including FTP, HTTP, SMTP, POP, IMAP, SNMP, LDAP, DNS, RSS, SMPP(SMS), XMPP (Jabber), SOAP, and WebDav. It includes source code for compilation on various Unix platforms, a framework for Objective-C (Cocoa) Mac OS X development, and native PHP extensions.
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.