Some time you might find some applications are having only .rpm files but you want a .deb package for your debian,Ubuntu and other debian derived ditributions.If you cant find .deb debian package in any of the debian,ubuntu repositories or elsewhere, you can use the alien package converter to install the .rpm file.
Alien is a program that converts between the rpm, dpkg, stampede slp, and slackware tgz file formats. If you want to use a package from another distribution than the one you have installed on your system, you can use alien to convert it to your preferred package format and install it.
Despite the large version number, alien is still (and will probably always be) rather experimental software. It has been used by many people for many years, but there are still many bugs and limitations.
Alien should not be used to replace important system packages, like sysvinit, shared libraries, or other things that are essential for the functioning of your system. Many of these packages are set up differently by Debian and Red Hat, and packages from the different distributions cannot be used interchangably. In general, if you cant uninstall the package without breaking your system, dont try to replace it with an alien version.
Install alien in debian
#apt-get install alien
This will install all the required packages.Now you can start converting your .rpm files to .deb packages.
Available Options for alien
Convert the package.rpm into a package.deb
#alien -d package-name.rpm
Convert the package.rpm into a package.deb, and install the generated package.
#alien -i package-name.rpm
If you want to keeps alien from changing the version number use the following command
#alien -k rpm-package-file.rpm
Example
Suppose we have a avg antivirus avg71lms-r30-a0782.i386.rpm file
To convert .rpm to debian
#alien -k avg71lms-r30-a0782.i386.rpm
Now you should be having avg71lms-r30-a0782.i386.deb file
To install .deb file
#dpkg -i avg71lms-r30-a0782.i386.deb
If you dont use -k option you should see avg71lms_r30-1_i386.deb file the difference is it will add 1
Install alien in Ubuntu
$sudo apt-get install alien
You can check the above section for available options
Example
Suppose we have a avg antivirus avg71lms-r30-a0782.i386.rpm file
To convert .rpm to debian
$sudo alien -k avg71lms-r30-a0782.i386.rpm
Now you should be having avg71lms-r30-a0782.i386.deb file
To install .deb file
$sudo dpkg -i avg71lms-r30-a0782.i386.deb
If you dont use -k option you should see avg71lms_r30-1_i386.deb file the difference is it will add 1
courtesy http://anhblog.net/pc-place/linux-unix/howto-install-rpm-files-on-debian-and-ubuntu/
Articles 
