The following sources are more suitable for CERNET, where both Netease And Sohu are available.
Modify/etc/APT/sources. List
Sudo apt-Get gedit/etc/APT/sources. List
# Source of Emy of electronics
Deb http://ubuntu.uestc.edu.cn/ubuntu/ lucid main restricted universe multiverse
Deb http://ubuntu.uestc.edu.cn/ubuntu/ lucid-backports main restricted universe multiverse
Deb http://ubuntu.uestc.edu.cn/ubuntu/ lucid-proposed main restricted universe multiverse
Deb http://ubuntu.uestc.edu.cn/ubuntu/ lucid-security main restricted universe multiverse
Deb http://ubuntu.uestc.edu.cn/ubuntu/ lucid-Updates main restricted universe multiverse
The Deb-Src http://ubuntu.uestc.edu.cn/ubuntu/ lucid main restricted universe multiverse
Deb-Src http://ubuntu.uestc.edu.cn/ubuntu/ lucid-backports main restricted universe multiverse
Deb-Src http://ubuntu.uestc.edu.cn/ubuntu/ lucid-proposed main restricted universe multiverse
The Deb-Src http://ubuntu.uestc.edu.cn/ubuntu/ lucid-security main restricted universe multiverse
The Deb-Src http://ubuntu.uestc.edu.cn/ubuntu/ lucid-Updates main restricted universe multiverse
# New Source of zhongke University
Deb http://debian.ustc.edu.cn/ubuntu/ lucid main multiverse restricted universe
Deb http://debian.ustc.edu.cn/ubuntu/ lucid-backports main multiverse restricted universe
Deb http://debian.ustc.edu.cn/ubuntu/ lucid-proposed main multiverse limit universe
Deb http://debian.ustc.edu.cn/ubuntu/ -Security main multiverse restricted universe
Deb http://debian.ustc.edu.cn/ubuntu/ lucid-Updates main multiverse restricted universe
Deb-Src http://debian.ustc.edu.cn/ubuntu/ lucid-backports main multiverse restricted universe
Deb-Src http://debian.ustc.edu.cn/ubuntu/ lucid-proposed main multiverse restricted universe
Deb-Src http://debian.ustc.edu.cn/ubuntu/ lucid-security main multiverse restricted universe
Deb-Src http://debian.ustc.edu.cn/ubuntu/ lucid -Updates main multiverse restricted universe
Netease source
Deb http://mirrors.163.com/ubuntu/ lucid main restricted universe multiverse
Deb http://mirrors.163.com/ubuntu/ lucid-security main restricted universe multiverse
Deb http://mirrors.163.com/ubuntu/ lucid-Updates main restricted universe multiverse
Deb http://mirrors.163.com/ubuntu/ lucid-proposed main restricted universe multiverse
Deb http://mirrors.163.com/ubuntu/ lucid-backports main restricted universe multiverse
Deb-Src http://mirrors.163.com/ubuntu/ lucid main limit universe multiverse
Deb -Src http://mirrors.163.com/ubuntu/ lucid-security main restricted universe multiverse
Deb-Src http://mirrors.163.com/ubuntu/ lucid-Updates main restricted universe multiverse
Deb-Src http://mirrors.163.com/ubuntu/ lucid-propomain sed restricted universe multiverse
Deb-Src http://mirrors.163.com/ubuntu/ lucid-backports main restricted universe multiverse
# Source of Sohu
Deb http://mirrors.sohu.com/ubuntu/ lucid main restricted
Deb-Src http://mirrors.sohu.com/ubuntu/ lucid main restricted
Deb http://mirrors.sohu.com/ubuntu/ lucid-Updates main restricted
The Deb-Src http://mirrors.sohu.com/ubuntu/ lucid-Updates main restricted
Deb http://mirrors.sohu.com/ubuntu/ lucid universe
Deb-Src http://mirrors.sohu.com/ubuntu/ lucid universe
Deb http://mirrors.sohu.com/ubuntu/ lucid-Updates universe
Deb-Src http://mirrors.sohu.com/ubuntu/ lucid-Updates universe
Deb http://mirrors.sohu.com/ubuntu/ lucid multiverse
Deb-Src http://mirrors.sohu.com/ubuntu/ lucid multiverse
Deb http://mirrors.sohu.com/ubuntu/ lucid-Updates multiverse
Deb-Src http://mirrors.sohu.com/ubuntu/ lucid-Updates multiverse
# Beijiao update source
Deb http://mirror.bjtu.edu.cn/ubuntu/ karmic main multiverse restricted universe
Deb http://mirror.bjtu.edu.cn/ubuntu/ karmic-backports main multiverse restricted universe
Deb http://mirror.bjtu.edu.cn/ubuntu/ karmic-proposed main multiverse limit universe
Deb http://mirror.bjtu.edu.cn/ubuntu/ karmic -Security main multiverse restricted universe
Deb http://mirror.bjtu.edu.cn/ubuntu/ karmic-Updates main multiverse restricted universe
Deb-Src http://mirror.bjtu.edu.cn/ubuntu/ karmic-backports main multiverse restricted universe
Deb-Src http://mirror.bjtu.edu.cn/ubuntu/ karmic-proposed main multiverse restricted universe
Deb-Src http://mirror.bjtu.edu.cn/ubuntu/ karmic-security main multiverse restricted universe
Deb-Src http://mirror.bjtu.edu.cn/ubuntu/ karmic -Updates main multiverse restricted universe
# Wuhan University self-improvement network
Deb http://mirror.ziqiang.net/ubuntu/ jaunty main restricted universe multiverse
Deb http://mirror.ziqiang.net/ubuntu/ jaunty-backports main restricted universe multiverse
Deb http://mirror.ziqiang.net/ubuntu/ jaunty universe multiverse
Deb http://mirror.ziqiang.net/ubuntu/ jaunty-security main restricted universe multiverse
Deb http://mirror.ziqiang.net/ubuntu/ jaunty-Updates main restricted universe multiverse
Deb-Src http://mirror.ziqiang.net/ubuntu/ jaunty main restricted universe multiverse
Deb-Src http://mirror.ziqiang.net/ubuntu/ jaunty-backports main restricted universe multiverse
Deb-Src http://mirror.ziqiang.net/ubuntu/ jaunty-proposed main restricted universe multiverse
Deb-Src http://mirror.ziqiang.net/ubuntu/ jaunty
Deb-Src http://mirror.ziqiang.net/ubuntu/ jaunty-Updates main restricted universe multiverse
# submitted source
Deb http://ftp.sjtu.edu.cn/ubuntu/ lucid main multiverse restricted universe
Deb http://ftp.sjtu.edu.cn/ubuntu/ lucid-backports main multiverse restricted universe
Deb http://ftp.sjtu.edu.cn/ubuntu/ lucid-proposed main multiverse restricted universe
Deb http://ftp.sjtu.edu.cn/ubuntu/ lucid-security main multiverse restricted universe
Deb http://ftp.sjtu.edu.cn/ubuntu/ lucid-Updates main multiverse extends universe
Deb http://ftp.sjtu.edu.cn/ubuntu-cn/ lucid main multiverse restricted universe
Deb- SRC http://ftp.sjtu.edu.cn/ubuntu/ lucid main multiverse restricted universe
Deb-Src http://ftp.sjtu.edu.cn/ubuntu/ lucid-backports main multiverse restricted universe
Deb-Src http://ftp.sjtu.edu.cn/ubuntu/ lucid-proposed main multiverse restricted universe
Deb- SRC http://ftp.sjtu.edu.cn/ubuntu/ lucid-security main multiverse restricted universe
Deb-Src http://ftp.sjtu.edu.cn/ubuntu/ lucid-Updates main multiverse restricted universe
(original address: http://blogold.chinaunix.net/u3/113413/showart_2225679.html)