Frustratingly my laptop has Rails 3 on it, although I cannot find much supporting documentation on how to use Rails 3, excepting the API reference.
There appears to be a significant amount about regarding rails 2.2. Would you recommend downgrading and learning 2.2 or just plough ahead with 3 and hope for the best?
If you don't have any experience yet, you'd better start with the latest version. As for no documentation, how about Rails Guides? I think that's pretty awesome.
If you really are stuck with Rails 3, at least use Rails 2.3.x instead of 2.2.
Highly recommend continue with Rails3. No new apps out there are going to be created with Rails 2.3 -- as gems and engines are created and updated, your 2.3 app will get out of date.
The documentation is still coming for Rails3 out on the blogosphere, but searching for "Rails3 where conditions" gives good rails3 results.
If you're willing to buy documentation, Agile Web Development with Rails (4th edition) was quite excellent in its first edition, and was how I learned. Its 4th version covers rails 3.
Rails tends to move pretty fast, so it hard for the documentation to keep up. This is a known problem though, and http://railstutorial.org/ was made to be a comprehensive tutorial that will be maintained by the rails evangelism team. (you can buy the book/screencast, or just go to the "book" link on the menubar, it is freely available there)
Rails 3 was a great release, I would recommend sticking with it if at all possible.
As captaintokyo and Jesse Wolgamott I strongly encourage you to use Rails3. Another great ressource to learn about Rails3 is http://railstutorial.org/ .
I agree, start learning on Rails 3. Everything is moving that way quickly.
If you knew you were going to be working on rails 2.* applications (you were starting a new job next month and they had rails 2 apps already installed and were not upgrading them this year) is the only reason I would give to start with 2.*.