I use a very pretty radial tree of life diagram fairly often — the last time was in my talk on Friday — and every time I do, people ask where I got it. Here it is: it's from the David Hillis lab, with this description:

This file can be printed as a wall poster. Printing at least 54" wide is recommended.

(If you would prefer a simplified version with common names, please see below.)

Blueprint shops and other places with large format printers can print this file for you.

You are welcome to use it for non-commercial educational purposes.

Please cite the source as David M. Hillis, Derrick Zwickl, and Robin Gutell, University of Texas.

About this Tree: This tree is from an analysis of small subunit rRNA sequences sampled

from about 3,000 species from throughout the Tree of Life. The species were chosen based

on their availability, but we attempted to include most of the major groups, sampled

very roughly in proportion to the number of known species in each group (although many

groups remain over- or under-represented). The number of species

represented is approximately the square-root of the number of species thought to exist on Earth

(i.e., three thousand out of an estimated nine million species), or about 0.18% of the 1.7 million

species that have been formally described and named. This tree has been used

in many museum displays and other educational exhibits, and its use for educational purposes

is welcomed.

There's also a simplified version:

Both of those are available as scalable pdfs, so you can zoom in and out to get just the right view, which is very handy.