wget has a cool feature known as limit-rate.

If you want to leave a bit of bandwidth for other things then use it with double u get.

wget -c -t 100 --limit-rate=80k http://ftp.iinet.net.au/pub/ubuntu-releases/8.10/ubuntu-8.10-beta-desktop-i386.iso

The above means
-c retry from the last byte of the download if it fails, don't redownload the whole lot
-t retry this many times default is 20
--limit-rate this is how much bandwidth you want to restrict wget to. (in this case 80kilobits a second)
http://ftp.iinet.net.au/pub/ubuntu-releases/8.10/ubuntu-8.10-beta-desktop-i386.iso the file you want to grab.