Since the fall of 2008, I’ve been doing just about all of my web development on a MacBook Pro. Since switching from a PC to a Mac, I’ve found many replacements for software providing the common needs for web development on a PC. First off, with many choices out there for editors and development studios, I prefer Coda from Panic. It a single window development solution providing site management, code formatting and auto completion, integrated FTP / SFTP and SSH Terminal, plus many more features. Coda is not the only game in town though, Textmate and Espresso are both very well know and fully functional pieces of software as well.
With any development, there is absolutely no reason for you to not use Source Control Management (SCM) software to track changes and backup your programing. The aging standard is Subversion (SVN). For SVN, besides the command line, I have fallen in love with Versions. It provides a clean graphical interface to your SVN repositories and working copies. The more recently popular SCMs are Git and Mercurial. I’ve found Gitti and MacHg, respectively, to be useful frontend GUIs to the Git and Mercurial SCMs.
Almost all current websites or applications will have a database backend. In order to manage the layout and design of those databases along with content, you need a database manager. For a native client on a Mac, I use Sequel Pro for MySQL database management. One could also always use the web-based frontend phpMyAdmin to manage their databases as well, but this does not run natively on a Mac without a webserver running.
Last but defiantly not least, when you are developing, having to constantly save and upload your working files to a remote webserver can extremely slowdown development and testing times. That’s why having a local development environment is such a wonderful addition to a web developer’s toolkit. For Mac, MAMP and MAMP Pro provide this needed environment. Once installed, you will have a Mac Apache MySQL PHP webserver up and running your files locally. MAMP will provide a basic setup with just a single site for free, while MAMP Pro will add additional functionality to control and add additional sites to your install for $59. Normally XAMPP would be for Windows but they have created a version for the Mac. Even though technically still in beta, it runs very stable with several additional pieces that are sometimes desired on a webserver.
The bottom line here is that no matter if you are running a Windows, Linux, or Mac workstation, there are many solutions out there for a web developer to use. This is by no means a comprehensive list, as many more very useful and wonderful Mac applications exist to support developers’ produce their applications.