I've already used it in the previos post, but not mentioned it: HERE you find a great way to post LaTeX in your blog. It's very simple, just enter the formulas and copy the html-code into your blog.
The editor itself is great. It is fast and got many features like shortcuts to important commands and auto-closing brackets. Also, the result itself (the image) as well as the html-code is presented just in time!
Another important thing: it's open-source, so you can use it without any limitations (at least I haven't read something different yet).