If you are not getting a package on Ubunu using apt-get then chances are that it has not been updated in the /etc/apt/sources.list file

For example, the following should be there in the sources.list file if you are running Ubuntu 10.04 LTS (codename lucid)

## main & restricted repositories
deb http://us.archive.ubuntu.com/ubuntu/ lucid main restricted
deb-src http://us.archive.ubuntu.com/ubuntu/ lucid main restricted

deb http://security.ubuntu.com/ubuntu lucid-updates main restricted
deb-src http://security.ubuntu.com/ubuntu lucid-updates main restricted

deb http://security.ubuntu.com/ubuntu lucid-security main restricted
deb-src http://security.ubuntu.com/ubuntu lucid-security main restricted

## universe repositories - uncomment to enable
deb http://us.archive.ubuntu.com/ubuntu/ lucid universe
deb-src http://us.archive.ubuntu.com/ubuntu/ lucid universe

deb http://us.archive.ubuntu.com/ubuntu/ lucid-updates universe
deb-src http://us.archive.ubuntu.com/ubuntu/ lucid-updates universe

deb http://security.ubuntu.com/ubuntu lucid-security universe
deb-src http://security.ubuntu.com/ubuntu lucid-security universe

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