There is of course loads of chat about MVC and how to leverage it into web app design. I like the counter-point given by Andy Wordley here:

In fact, there are plenty of other design patterns that are equally, or
more relevant to web applications and to writing good, solid code that
clearly separates concerns. For example, the Chain of Responsibility
(to implement a pipeline processing model), Mediator/Facade (to abstract
internals behind clean interfaces to ease SOC), Strategy (to define
a general strategy for all web applications that can be specialised
for different requests), Abstract Factory and Factory Methods (to
allow different implementations to be switched in/out) and so on.