Gemse 1.0.11 has been published!
The project Gemse has been started in the need for an editor for mathematical formulas that is fast and can be controlled by keyboard only.
Actually, the first approach to this problem, "Gemse Approach 1", is an editor for Presentation and Content MathML. It is currently in development.
You can find other solutions on the software list of the W3C. Additionally there is Sentido which is used for example in the editor of SWIM (test it).