I am a manual functional tester and I am keen on shifting my career from Manual testing to Automation testing using Selenium. What is the best way to begin with this goal of mine? Thanks!
For all practical purposes you can ignore Selenium RC. Selenium WebDriver is the thing.
To learn scripting, you need to learn programming (it is the same thing). Python is commonly considered best for beginners (much easier to start coding than ie Java). Learning Python will allow you to solve all kinds of problems, not only testing automation (it is universal language). But it will take some significant mental effort to become a competent programmer.
There are plenty of free books and other resources to learn Python on internet, including free courses on Udacity and elsewhere. EdX.org is excellent (and free!) source for all levels comp-sci education, from beginner to MS level. And Python has good bindings and lively community for Selenium testing. It is a good choice, especially if you do not have a local programming guru to guide you. If you do, ask him/her to learn Python together :-)
It will make little sense to read about Selenium WebDriver until you are at least semi-competent programmer.
Few links about learning Selenium:
Then read docs, Google is your friend.
When you become competent programer you need to learn about design pattern, especially PageObject, but it is way ahead in your future. Good luck!
I assume that you have experience with one of the supported programming languages and a proper xUnit framework for unit tests. If not, choose one of of the programming languages and learn the basics and how to write unit tests. After that you can start with Selenium 2 / WebDriver. Apart from that it is very useful to install the Selenium IDE plugin for firefox to discover what Selenium do, if you don't know.
I also agree with Nils.
Here are some useful links:
Selenium RC is the older version, I think its obsolete. Focus on the Selenium Webdriver version, unless you need some specific feature the older RC version delivers. For a more detailed comparison see this question