BBEdit
The most useful tool is a text editor and on the Macintosh the only one to use is BBEdit.
I first started using it at version 3 and version 5.1.1 is a huge improvement over previous versions. There is wonderful integration with MacPerl and AppleScript now standard and the HTML tools are now accessible on the menu bar as well as via a tool pallette.
The MacPerl integration is wonderful. Not only can you run and debug scripts easily with BBEdit and MacPerl but it now has the ability built in to filter the selection through a MacPerl script. The syntax colouring is useful, if only for catching runaway strings and making my more obvious syntax errors stand out.
The web page creation facilities are amazing. You can define templates and includes and have BBEdit use them in constructing pages, it now has "cleaners" to remove extraneous tags left by the more popular WYSIWYG page editors and you can even include the output of a MacPerl script in your web page. Add to that syntax colouring, a pallete that allows easy insertion of HTML tags, a pop up window with HTML entities, and another that gives the "safe" colours for the web where you can drag a colour into your document and the right RGB values will be inserted (nice trick). If you're a fossil, like me, who has use for it there is even an ASCII table window.
It has excellent search and replace (using regular expressions if you wish), always a must with a text editor. I've even used this to filter logs; I just remove all lines with the server name and address in them to remove the internal refers then sort the file, often I have one site sending me a lot of direct links so filter those out the same way. This then makes it very easy to spot where you're getting your refers from. If the search and replace isn't capable of doing what you need then you can always fall back to some MacPerl hacking and write a filter.
At $US119 BBEdit it isn't exactly cheap, but it is one investment that will pay for itself.

