How to Create Figures for Latex
This information was shamelessly stolen from Leo Reyzin's more extensive explanations. After looking for a very long time, this is the first solution that works really easily and nicely (I have Acrobat professional so I have no problem with this solution; if you don't have it I suggest buying it - the academic price is very reasonable).
This method assumes that you have Adobe Acrobat (not just the Reader, but the actual Acrobat) installed on your machine.
Convert you PowerPoint slide to .pdf (you can just do "Save As PDF").
Open the .pdf file in Adobe Acrobat Professional. Delete all the pages but the one that contains your picture (use Document->Delete Pages). Then crop the remaining page so that only the picture is left on it (Document->Crop Pages); use the Margin Controls to do this (lines will appear as you change the values).
Save the file: select File->Save As, and select "Encapsulated PostScript (.eps)" under the file type, to save the same file as an .eps.
Insert into your LaTeX document using the \includegraphics command of the graphicx package (be sure to not specify the file extension in the command; that way, it will compile with both latex (using the .eps) and the pdflatex (using the .pdf)).