I think, that MathML works, but it is not very effective.
If you have a Mathtype software, MS Office (MS Office installed before MathType) then there is no problem. You are able to copy Maple output to MathType window that is occured from Office using Inserting Equation from the menu. It works and the result is editable in the powerpoint (all office products). I do not know the reason why use MathML or other technologies instead of OLE on Windows platform. It works!
The second way is use OpenOffice and its Math editor but there are some problems.
MathType is able to import a LaTeX source and it converts the input to Math-2D formula, MathML too.
Of course, MathType is usually not installed on machines at conferences. If you use your machine, why you not use Maple presentation mode directly?