Robby Russell is a constant source of information on Ruby and Rails, I have used his instruction on how to set up Rails and PostgreSQL on Mac a number of times. It is therefore fun to see that I have actually used 3 out of the 5 things he wants to know more about::
RSpec User Stories
We were very early adopters of this one, we started using it the same day it hit trunk in a useable form. Everyone should start using it today - I cannot speak highly enough of it. The only thing I miss is a Fit-style table approach to rules, but I have my own thoughts about that one.
Using Selenium with RSpec
We have used the now outdated spec/ui library at WeMind. Today we use RSpec Stories almost exclusively for acceptance testing. My position is to use Selenium only where you really need it, for example to test Javascript functionality.
JQuery
I have used it for the dynamic hiding of speaker info for Agila Sverige. Not at all enough to judge a library by, but it feels a lot sweeter than Prototype/RJS.
JSSpec (BDD for Javascript)
Yeah, I wanna know more about this as well.
Using the Google Charts API with Rails
Same here.
Other than that I would love to try out: