TexNicCenter is free and pretty easy to use. (I'm not sayin' that is the best.)
Actually, this is what makes Latex so powerful and easy to use. Once you get used to it, you can create portable documents that look much better than MS Word in a short time, without using those messy menus, options, right clicks etc..
Well, what do you want to do with Latex? Are you writing articles? Or do you just need little mathematical expressions in image format, like in this forum? If you're writing articles, you must install Latex to your pc and use an editor. Here, this will help you installing Miktex and Texniccenter. If you want to render math equation images, this site (or this site) is probably what you're looking for
If you're only doing the odd equation it's fine. You type your LaTex, click submit, right click on the image, copy and paste it where you want it.
This would be a pain if you wanted to do much though.