Leibniz for Mac

From DirectMath:

Leibniz is a graphical front end to Mathematica on Macintosh and Windows computers which allows you to type mathematical text and carry out calculations using a simple, drag and drop style of expression manipulation. Leibniz is a mathematical word processor: it allows you to quickly and easily type text and structured mathematical expressions. You can launch calculations from within Leibniz by selecting an expression to evaluate andhitting enter, or by selecting a portion of an expression and dragging it around the expression to launch a calculation. Leibniz uses MathLink tocommunicate with the Mathematica kernel, sending expressions to Mathematica for evaluation and translating the results back into nicely formatted mathematical expressions.