I stumbled across this site recently and found it very useful for
learning Ruby syntax and programming in general.
There are hundreds of short Ruby programming puzzles that you do
interactively on the site. You get scored on your solutions and the
problems are labelled for difficulty and type.
Although there are a lot of puzzles, it needs more! so please submit one
if you have the time.
I find doing these short simple puzzles very helpful for retention.
Some other short Ruby puzzle sites that I have found:
http://rubymonk.com/ (very slick site, as good as Rubeque)
http://rubykoans.com/
GitHub - ryanb/ruby-warrior: Game written in Ruby for learning Ruby and artificial intelligence. (coding practice in the form of a
game - supposed to be good but I haven’t managed to get it working yet,
dunno how to load gems)
Similar sites, non-ruby:
http://projecteuler.net/ (not language specific, problems take longer to
solve)
http://codingbat.com/ (Java and Python)