I have used a couple of macro filters which use the filter mount on the end of the lens. I've actually been quite happy with them. They're very inexpensive and if you want to try things out a bit without committing to a big purchase then it's not a bad option.

I tend to do a pretty big range of nature photography and the flexibility of adding macro without carrying a lot of additional lenses is a big plus. Of course, if you're confident that you'll be doing a lot of macro work then it may be worth it to bite the bullet and get the appropriate lenses because the result is not going to be as good otherwise(slower, focal range, etc).

Of course, this is not the same as a reverse macro ring which, admittedly, I don't have a lot of experience with. Of note, there seems to be a great deal of info on making your own (e.g. http://www.diyphotography.net/diy_reverse_macro_ring and the extreme http://jyoseph.com/diy-macro-lens-reverse-mount-extension-tube/).