For the Ruby dev positions, be prepared with a few links to open source Ruby projects you've written on Github et al, or contributions to open source projects. Not a hiring strategy I'd agree with, but I guess that's what they've decided on.

I asked if they'd do a 'challenge' of some sort, but they didn't like that approach, and returned with 'Please look at our buglist and submit a patch then'. I find that quite an inventive way to get your defects looked at.