The standard tool for such cases is called "alien", and it's available for most distros by default. This is the site if you really care about it (you shouldn't need to visit it, as said, use your package manager to install it).
http://kitenet.net/~joey/code/alien/
The above is the response to your question, the following is some information that I strongly believe that you should at least consider.
Converting a package to another archive format doesn't guarantee at all that the package is going to be compatible with your distribution. As a general rule, packages made for one distro shouldn't be used on another distribution, unless you enjoy fixing your system or reinstalling every month.
So, you should stick to packages designed for your distribution. If you can't find an official package for your distribution, you should look into the site of the authors of the software, sometimes they provide packages for a number of distributions. If there's absolutely no way to find a native package for your distribution, you should create your own, and if you are lazy, as the last resort, build it by hand and install it into a separate prefix under your home or in an alternate place like /usr/local/
