How does thinking on design patterns and OOP practices change in dynamic and weakly-typed languages?

Question

There is a fairly helpful question already along these lines ("Non-OOP Design Patterns?"), but I am more curious about a transitional point of view for someone just getting started with dynamic and weakly-typed languages.

That is: let's say I've been programming in C++, C#, or Java for many years, and absorbed lots of wisdom along the lines of the GoF design patterns, Fowler's Patterns of Enterprise Application Architecture, SOLID principles, etc. Now I'm dabbling in Ruby, Python, JavaScript, etc., and wondering how my knowledge applies. Presumably I could do direct translations in many cases, but almost certainly that wouldn't be taking full advantage of my new setting. Duck typing alone turns a lot of my interface-based thinking on its head.

What stays the same? What changes? Are there guiding principles like SOLID, or canonical patterns (perhaps entirely new ones) that a dynamic language newbie should know?