I think it depends on the nature of the application.
If it’s for casual personal use, just about any of the distros would do. I’d use the latest stable release. I happen to like Fedora.
If it’s for a more important personal use or a non-critical business use, I’d use Centos. It’s a Red Hat Enterprise Linux derivative, essentially RHEL without support.
If it’s a mission-critical business application, I’d buy a RHEL 5.3 license to get the ongoing technical support.
Some folks might recommend SUSE/SLES instead of RHEL and I think that would be a valid option, too.