Welcome to LQ.
Quite simple :
1) su
2) alien -r <package.deb>
.. will create <package.rpm>.
But non CentOS packages will not always work,
you may miss some dependencies, only found in
other debian packages.
The correct way is to find it with 'yum search'
or rebuild it to rpm from a src.rpm or other source.
No 'alien' ? Then
http://packages.debian.org/lenny/alien
> Links for alien > > [alien_8.72.tar.gz]
.....