Jen just scored a new Powerbook as a graduation present (and is thus finally making the switch). She had asked me for a few pointers on some Mac software that I consider productivity essentials. Here are a few of the high points, roughly categorized:

Personal Information Management:

I use Tinderbox right now primarily for my web activities, but there is a much bigger potential in terms of writing and research. While an insanely useful piece of software, there are still holes that are filled by the Devon Technologies products.

The suite of products from Devon Technologies, DevonThink and DevonAgent are also part of my work flow. I really find the ability to browse a site with DevonAgetnt, especially a journal or conference repository and suck down useful bits of information into DevonThink, where I can then classify and organize. This is a recent purchase, so I am still trying to find the best workflow for the PhD.

TeX:

Once I have the information, I need to do something with it. In my case, this usually involves writing in LaTeX. For OSX, I use TeXShop for all my TeX needs. Good editor plus handy preview is really what it is all about. Oh, and now that I am on Tiger, the editor is much snappier than it used to be thanks to the performance improvements in the new OS.

With writing comes references, and for OSX the best BibTeX editor is BibDesk. Each update gets better and better. Recent additions are auto-generation of cite keys, auto-renaming and filing of pdfs, and a quick-input tool to help fill in the bibliographic information in the first place (always the most tedious).

Equation Service is a neat OSX Service that allows you to enter a snippet of LaTeX, and produce a small PDF of the equation as output. Great for putting nice-looking equations into applications that do not support LaTeX.

General OSX:

For general ssh work, SSH Keychain keeps things organized. Quicksilver is a fantastic system tool for launching applications, among its myriad uses. SubEthaEdit is a good general-purpose editor that is free for personal use.

I'm sure there are others, but these seem to be fired up most of the time (translation: right now).