For the most part anything you can get on Windows is probably available for the Mac... like Photoshop, Illustrator, Freehand, Dreamweaver, GoLive, etc. Some of the smaller shareware/free tools aren't cross platform but most likely there is an equiv of that for each platform.
But, like any kind of design, one program just isnt enough to do everything. Like I said above, I use Nvu (free, nice) and Dreamweaver. But I also use BBEdit for text editing, Transmit for uploading files, Photoshop Elements for cleaning up and editing graphics, Fireworks for spot compression, Flash for interactive elements as needed, and more. There are so many little tools that are invaluable as well that one needs to just play around and see what work for you.
I have been doing design for a long time (early 90s? wow im old), and I am always learning new stuff. Like I learned some PHP and MySQL finally in the last year to do a database site. It's one of the things I love about web design over print design, there is always something new to learn, new ways to design, new styles to pick up, tricks and secrets, etc.
And with the internet, you can pick up ideas, and exchange outlooks all with the magic of forums like these and who knows what you might come up with as a result.
Afterall... Everyone has their own methods but we all get to the same place eventually.