So here's where I'm coming from:  
My background is in C#, C++, VB Script, php, javascript, PowerShell, T-SQL, and VB 6.  I have some experience with python, and a brief introduction to Ruby On Rails.  At work, we're transitioning to a web based UI in the next year or so, but in asp.net & SilverLight.  I would like to, if possible, learn more open source web technologies on the side.  And, hopefully, in a year and a half or so, I would like to transition to a more open source web technology position.  I found that I do really like python, but I'm open to pretty much anything.  And yes, I do know Linux (ubuntu and gentoo), as well.  
And, here's my question:  
What technologies, frameworks, IDEs, or systems should I be highly proficient in to become a prime candidate for a position doing web application development using non-Microsoft technologies?