Texmacs is a free visual text editor for mathematics that can be used to produce TeX output. It also supports interactive use with various symbolic algebra programs, such as Macaulay2. Texmacs is available from http://www.texmacs.org/.
Be sure to get TeXmacs version 126.96.36.199 or later. There is bug in 188.8.131.52, the effect of which is that no output from Macaulay2 will be displayed.
Using TeXmacs as an interface to Macaulay2 is described in the TeXmacs online manual: http://www.texmacs.org/tmweb/manual/webman-interface.en.html. The basic procedure is to pull down the Insert menu, select Session from it, and then to select Macaulay2 from the resulting submenu. Alternatively, you can click on the icon that looks like a computer terminal and select Macaulay2 from the resulting submenu.
The interface is implemented by a special top level mode in Macaulay2 that causes the output to be converted to mathML, see TeXmacs. MathML conversion methods have not been implemented yet for all data types.