The title says it all – visit the download page for 1.8 to get it.  Most every mirror appears to have it right now – not just the ones on the 1.8 page.

Note that some sites have an early version of the 1.8.1 release that lacks the installer; that image is ‘dfly-1.8.1.iso.gz’.  Instead, be sure to download ‘dfly-1.8.1_REL.iso.gz’, which should be the newer file of the two.