Helps

Rails Shopping Carts

“Can anyone recommend a good Rails shopping cart?”

Spree was mentioned as reasonable suitable, but it does not support multiple merchants.

Interestings

Modernizer < 2.0 hates IE7

A Pivot was experiencing Modernizer at versions less than 2.0 throwing insecure content exceptions because of version detection code that it was using. Upgrading to version higher than 2.0 or removing Modernizer solved the problem.

Resque and New Relic outstanding but

There is a bug when using RPM contrib in New Relic while also using Resque that causes Resque workers to die. Definitely something to watch out for.