The actuaries have issued a pretty decent document titled A New Approach for Managing Operational Risk which combines the basic risk management content for newbies with the right about of quant-type stuff. The document also makes some interesting distinctions between traditional and modern operational risk management and is worth a look.

http://riskczar.files.wordpress.com/2009/12/a-new-approach-for-managing-operational-risk_actuaries-riskczar.pdf

I am not a huge fan of quantifying operational risk so look for my rant about this.