Alien, the Linux application that converts between Red Hat rpm, Debian deb, Stampede slp, Slackware tgz, and Solaris pkg file formats now has a front-end GUI to simplify the already simple process of converting packages from one format to the other with Alien.
Alien is particularly useful in converting working .rpm packages to Debian/Ubuntu .deb format and vice-versa.
Package Converter, the front-end GUI for Alien is intuitive and easy-to-use, if you want to use a package from another Linux distribution than the one you have installed on your system.
Package Converter is written with Realbasic and has downloadable packages in BIN, RPM and DEB. It requires Alien — it goes without saying.