Description: I would like to suggest the .7z archive as a default within the upload.php because "usually 7-Zip compresses to 7z format 30-70% better than to zip format. And 7-Zip compresses to zip format 2-10% better than most of other zip compatible programs." (http://www.7-zip.org/)
Many people I know are now using 7-Zip which is free software distributed under the GNU LGPL (except for the RAR plugin). Although it still might be for most people not commonly known and therefore not very important, it would be still very nice.