> Is there any recent tutorials?

An update to Vince's wonderful todo tutorial is brewing on 
http://rails.hieraki.org/. Along side it, you'll find a tutorial for 
testing with Rails. And documents on what's new in .9 and how to 
upgrade from .8 to .9.

I'm also planning to redo the original video for .9. Originally, it was 
a 10-minute thing. I'm confident that should be able to boil down to at 
least half with all the new productivity enhancements and use of 
WEBrick instead of Apache.

> One other question is, what would be better database to use with ruby 
> in term of support and active development -- MySQL or PostgreSQL?

I'm personally on MySQL, but have SQLite and PostgreSQL installed for 
testing as well. And there are plenty of Rails hackers working with 
PostgreSQL. So if you need a lot of features from the database, like 
stored procedures, views, triggers, and what have you, then PostgreSQL 
is the way to go. If you don't care too much about that, I've found 
MySQL easier to work with (but lets not get into that.. take it as a 
statement of preference, not fact ;)).

> I know that many has manage quite easily to use MySQL with PHP. Thanks

Basecamp is running MySQL. All my new projects are running MySQL. 
People have success with both MySQL and PostgreSQL. Talking about one 
being "better" than the other is unhelpful, imho.
--
David Heinemeier Hansson,
http://www.basecamphq.com/   -- Web-based Project Management
http://www.rubyonrails.org/  -- Web-application framework for Ruby
http://macromates.com/       -- TextMate: Code and markup editor (OS X)
http://www.loudthinking.com/ -- Broadcasting Brain