Gimp select rectangle selection as new image

I have already spent a few hours of time with this including on a gimp help forum and the gimp http://docs.gimp.org/en/ site (which has been down for a few days.)

I would like to use the rectangle selection tool to save a part of an image as a new image. I have not been able to do this so far. It is probably a simple answer. I have done just a few nice things with Gimp and have a few nice images on sites (and my avatar) to show for it.

The closest I got was being able to save the left column of pixels as an image, but then when I used it as a repeating image on a site it had about 299 px of white background with it, so you only see the image I wanted to repeat every 300 px. (dammit)

It is saved as a png image which is supposed to not include any background, at least according to one site I read. (snarl) ( we do need a set of snarlies to help balance out all the %#*&ing smilies, at least for my posts.)

So, to make a tedious story short, anyone know how to do this?

Edit: Actually I have done it before and been able to save the selected area just by clicking in it, but that is doing some different things to me now. Must have changed a setting somewhere?