Your question was very helpful to me in getting LaTeX working with Anki, but I've found there's an easier way to get dvipng:

1. Install MacTeX. I installed BasicTeX-2011.pkg and MacTeX-Additions-2011.mpkg, but I don't know if the latter is really required.
2. Use the TeX Live Utility to install dvipng: Go to Applications > TeX > TeX Live Utility. Click on the "Manage Packages" tab, search for "dvipng" and install it.

Once you do that, you should be all set.

Your question was very helpful to me in getting LaTeX working with Anki, but I've found there's an easier way to get dvipng:

1. Install MacTeX. I installed BasicTeX-2011.pkg (MacTeX-Additions-2011.mpkg is NOT required).
2. Open the terminal, type "tlmgr update --self && tlmgr install dvipng" and press enter. It will update TeX Live Manager and install the latest dvipng.

Once you do that, you should be all set.