Many of the major brands also stratify their offerings.

So, for example, you can find the Domane and Emonda in either Carbon Fiber or Aluminum depending on the sub-model.

I think Fuji is also strong with their Aluminum offerings.

Personally I've more or less skipped from steel to carbon fiber (and titanium), and have more or less skipped over aluminum. However, hopefully next week I'll be working on an aluminum frame with CF b-stays and CF fork.