Debian 5 Lenny is an excellent desktop or server option that is worthy of consideration. I have been running the Debian 5 Lenny candidate for awhile and have been very pleased with the stability and features. Read more here
Debian has a philosophy that is more like Red Hat/CentOS in that the focus is more on testing to insure stability of the whole system than to provide the latest and greatest applications. Debian comes with 18,733 packages. Debian 5 Lenny will have 5 DVDs to download with those packages, that is simply beyond any other distribution. These packages are maintained by volunteers who cover the globe providing insight and thinking from various cultures and backgrounds.