If you want to install Fink on Leopard, you'll need to go to the source release page because There is not currently a binary release for you. (Quote from the download page).
Download the package and follow the instructions found in INSTALL.html.
If you get a message like:
Use of uninitialized value in string ne at /sw/lib/perl5/Fink/Engine.pm line 1579.
like that happened to me after I wanted to install a package, run:
and that will fix it. It looks like somebody run into the same problem on the Fink user list.
The list of packages can be found here.
MacPorts has been updated to version 1.6 recently and the web site also looks like it has been updated. The install procedure for Leopart users is straightforward. Just click on the "Installing Mac Ports" and follow the instructions.
The list of available ports is here.