There are a number of questions on StackOverflow regard MVC best practices, but most of those seem to revolve around things like using Dependancy Injection, or creating helper functions, or do's and don'ts of what to do in views and controllers.

My question is more about how to architect an MVC application. For example, we are encouraged to use DI with the Repository pattern to decouple data access from the controller, however very little is said on HOW to do that specifically for MVC. Where would we place the Repository classes, for instance? They don't seem to be model related specifically, since the model should likewise be relatively decoupled from the actual data access technologies.

A second question involves how to structure the layers or tiers. Most example applications (Nerd dinner, Music Store, etc..) all seem to use a single tier, 2 layer approach (not counting tests) that typically has controllers directly calling L2S or EF code. If I want to create a multi-tier/layer aplication what are some of the best practices there in regards to MVC?

This question is one-part standard q-a, but another part best-practices, so it could go either here or programmers.se, I am marking it CW. If you feel it would be better suited to programmers.se then it can be migrated.

EDIT: What happened to the Community Wiki option? It seems to be gone.