I'm a moderately competent Python programmer, and am considering working on my first web-app; it seems a very large number of FOSS webapp code is written in Ruby (i.e. Rails), and I suspect that might help with my learning curve (i.e. for building a decent, if useless webapp).
There is lots of material for learning Ruby on the interwebs ofcourse, but wondering if there are any particular tips / resources / approaches that might be handy in moving from Python to rails?
To start getting your head around the similarities/differences between Ruby & Python, you may want to take a look @ this page on ruby-lang.org. It is super basic, but at a minimum gives you the terminology & concept translation you may need to get started. I tend to learn new things best by making mental comparisons to concepts I am familiar with.
Michael Hartl's Ruby on Rails Tutorial is by far the best introduction to Rails I've been able to find online. It's very easy to understand what's going on if you've already got experience in web application development in general. Versions of the tutorial for Rails 2.3.8 and Rails 3 are available. The introduction also discusses learning Ruby first vs learning Rails first.
Not only does it teach how to use Rails, it explains common Rails conventions (the Rails Way). I think this, in particular, is what you are looking for. It also encourages the use of good practices such as git source control and test-driven development, which is cool.