Author of Presentations Application for writing notebooks with custom graphics, tables, dynamic displays and other aids. Author of ExtendUnits Application. Coauthor of Tensorial. All these available at my web site for a relatively modest price.
My current interest is learning Grassmann algebra and writing a GrassmannCalculus Application in conjunction with John Browne, whose Grassmann algebra work I consider to be absolutely top notch.
I am generally interested in Mathematica as an extended technical development, preservation, documentation and communication medium - as opposed, say, to a super graphical calculator or programming language.