Are there any OpenOffice.org/LibreOffice equation editor/makers, similar to MathType?
There are two other major open-source mathematical document editors, both more directly inspired by (La)TeX. LyX is a wysiwyg front-end for LaTeX and lets you insert literal bits of LaTeX if you need it. If you're going to eventually learn LaTex to write documents with serious mathematical content, LyX provides a gentle curve to introduce you to the concepts before jumping into the syntax. Another contender is TeXmacs, which as the name suggests is inspired by both TeX and Emacs.
In terms of core functionality, they're all equivalent. They're all (MathType, OO Math, the Microsoft offering, LyX, TeXmacs, …) based on Knuth's design for TeX anyway. In terms of ergonomy, you'll have to make up your own mind.