Convincing others of Ruby over Python and PHP
You're going to have a tough sell over python. GitHub is written in Ruby, not for ruby per se, by the way.
For python one has BitBucket (even though I do prefer git), as well as pypi.
Correct me if I'm wrong, but it sounds like you haven't looked at python code all that much.  (I've written buckets of both python and Ruby by the way) I find it much more readable, especially when you're working on code that's not your own.
Anyways, not really answering your question, and don't really want to contribute more to the flame war.
G'day folks. I'm trying to introduce Ruby at work, and a few people are interested. However, I've been asked to present the benefits of Ruby over Python and PHP.
I've broken this down into 2 parts:
1) show Python and Ruby's advantages over PHP;
2) show Ruby's advantages over Python.
The first is easy. I'll explain things like:

Everything's an object.
Python and Ruby are easier to read and write.

For the second, I'm thinking of:

Ruby has many conveniences, which makes it easier to read and write. Eg: Optional brackets, and being able to open built-ins, allows for things like 2.days.from_now
RSpec is miles ahead of Python's TDD and BDD frameworks.
GitHub and RubyForge are fantastic resources for finding, releasing, and collaborating on software.

Do you have any suggestions? I'm all ears!