MORE to Keynote
EquationService, if you haven’t seen it, is a handy free application which produces PDF images with PDFLATEX or CONTEXT that can be dragged and dropped into Keynote or almost any other Mac OS X application. The main advantage over using TeXshop or similar is that you can typeset a single equation to get a small PDF image containing only that equation, rather than an entire page. The interface sucks, however, and I sent the author some changes which I hope he incorporates.
There's more info on LaTeX in Keynote from Kai von Fintel.