The Release Candidate can be downloaded from the following mirrors (some mirrors may still be updating):
(please use bittorrent to download if possible). .torrent files are available alongside the CD images.
Africa
http://bw.releases.ubuntu.com/kubuntu/9.10 (Botswana)
http://mz.releases.ubuntu.com/kubuntu/9.10 (Mozambique)
http://sz.releases.ubuntu.com/kubuntu/9.10 (Swaziland)
http://ubuntu.mirror.ac.za/ubuntu-release/kubuntu/9.10 (South Africa)
http://zw.releases.ubuntu.com/kubuntu/9.10 (Zimbabwe)
Asia
ftp://ftp.corbina.net/pub/Linux/ubuntu-cd/kubuntu/9.10 (Russian Federation)
http://ftp.cse.yzu.edu.tw/pub/Linux/Ubuntu/ubuntu-cd/kubuntu/9.10 (Taiwan)
http://ftp.daum.net/ubuntu-releases/kubuntu/9.10 (Korea, Republic of)
http://ftp.linux.org.tr/ubuntu-releases/kubuntu/9.10 (Turkey)
http://ftp.twaren.net/Linux/Ubuntu/ubuntu-cd/kubuntu/9.10 (Taiwan)
Europe
http://nl.releases.ubuntu.com/releases/kubuntu/9.10 (Netherlands)
http://ftp-stud.hs-esslingen.de/pub/Mirrors/releases.ubuntu.com/kubuntu/9.10 (Germany)
North America
http://mirror.anl.gov/pub/ubuntu-iso/CDs/kubuntu/9.10 (United States)
http://less.cogeco.net/ubuntu-releases/kubuntu/9.10 (Canada)
http://linux.nssl.noaa.gov/releases/kubuntu/9.10 (United States)
http://mirror.csclub.uwaterloo.ca/ubuntu-releases/kubuntu/9.10 (Canada)
http://mirrors.ccs.neu.edu/releases.ubuntu.com/kubuntu/9.10 (United States)
http://mirrors.gigenet.com/ubuntu/kubuntu/9.10 (United States)
Oceania/Australia
http://ftp.citylink.co.nz/ubuntu-releases/kubuntu/9.10 (New Zealand)
http://ubuntu-releases.optus.net/kubuntu/9.10 (Australia)
http://mirror.internode.on.net/pub/ubuntu/releases/kubuntu/9.10 (Australia)
http://mirror.pacific.net.au/linux/ubuntu-releases/kubuntu/9.10 (Australia)
http://planetmirror.com/pub/ubuntu/releases/kubuntu/9.10 (Australia)
South America
http://espelhos.edugraf.ufsc.br/ubuntu-releases/kubuntu/9.10 (Brazil)
http://ftp.ucr.ac.cr/ubuntu-cd/kubuntu/9.10 (Costa Rica)
Rest of the world
http://releases.ubuntu.com/kubuntu/9.10 (Great Britain)
DVDs
Checking iso
Its always best to check cd image before install! Check the md5 with comand md5sum /path/iso or for cd md5sum /dev/sr0. More information on how to check your iso can be found here
MD5sums for the RC:
kubuntu-9.10-rc-alternate-amd64.iso: d6a2142ef0ae39ea482a571ef4fa2e54
kubuntu-9.10-rc-alternate-i386.iso: 2006a850ecf74321b8651e9806419667
kubuntu-9.10-rc-desktop-amd64.iso: c7b400031464381bca7c051e94041756
kubuntu-9.10-rc-desktop-i386.iso: eb1cd70846f853aa0c4072b0ce1eb392
kubuntu-9.10-rc-netbook-i386.iso: *kubuntu-9.10-rc-netbook-i386.iso