That depends on exactly what you mean by full/wide technical support. If you mean support packages that you pay money for, then the first one that comes to mind is Red Hat. There is also SUSE, although I have some bad feelings about that distro, and can't recommend it. Canonical has paid desktop and server support packages for Ubuntu. (http://www.ubuntu.com/support/paid). Mandriva has phone support as well, although its a bit pricey (http://store.mandriva.com/?cPath=27).
There are other distributions that have free support all over the internet -- documentation, forums, mailing lists, and that sort of thing. Ubuntu has a lot of that (because they have such a large user base), as well as Debian. Fedora also has lots of support, although it is not one of the most beginner-friendly distros out there (I hear). Mandriva has some wikis and mailing lists.
All of this depends a bit on what you are looking for. If you're trying to set up a an enterprise level linux network, you may want to head in the direction of some kind of Redhat enterprise package, or a custom solution from a vendor like IBM.
PerlCoder (http://www.indicium.us)