I downloaded the latest Raspbian image from the raspberrypi.org website on my Mac running OS X 10.10.5 The SHA-1 checksum agrees with that listed on the website.
When I try to extract using
unzip I get the following error
warning [2015-09-24-raspbian-jessie.zip]: 76 extra bytes at beginning or within zipfile (attempting to process anyway) error [2015-09-24-raspbian-jessie.zip]: reported length of central directory is -76 bytes too long (Atari STZip zipfile? J.H.Holm ZIPSPLIT 1.1 zipfile?). Compensating... skipping: 2015-09-24-raspbian-jessie.img need PK compat. v4.5 (can do v2.1) note: didn't find end-of-central-dir signature at end of central dir. (please check that you have transferred or created the zipfile in the appropriate BINARY mode and that you have compiled UnZip properly)