I want an equation-writing tool that will let me write equations in posts and email. I'm making progress, but still don't have something that's as easy as I want.
I found OpenOffice Math (oomath) will let me do stand-alone equation generation, and gives me the option to save the result as MathML. If I name the output file "whatever.xhtml" it displays just fine as a web page, in Firefox.
It won't, however, let me cut-and-paste into email or into blogger posts.