Here’s something I found out while surfing around which I though may be of interest to some (only Canon users though!). If you buy a really cheap 35-80mm lens like
this from E-bay and whip out the front focusing elements it makes a pretty decent macro lens.
Pro’s are; it’s probably cheaper than a set of tubes and you can control the aperture (unlike cheap tubes).
Con’s are; very small minimum focus distance around 5cm which is OK for flies but probably not so good for bugs and no focus method (you have to move the camera to focus).
More details are
here
Cheers - Steve