Update: This was renamed to campaign_monitor_party.
First of all, HTTParty is simply amazing. That is all.
Second, Ruby never ceases to amaze me regarding its power and tools for meta-programming. "method_missing" is just too cool.
Third, I created a 20-line wrapper class for the Campaign Monitor API this weekend (using HTTParty). The code and the gem is over on GitHub: http://github.com/seven1m/campaign_monitor_party.