A series of dropdowns isn’t necessarily bad. The example you gave with cars is very well-suited to this type of navigation due it its hierarchical structure, and it’s seen on many websites. www.edmunds.com and www.tirerack.com both use this technique.
In both cases they use AJAX to dynamically fill the next dropdown list after the Make is selected, and in the case of TireRack, they expand yet again after the Model is selected to display trim levels. This makes the UI very responsive. Because it’s so common, users accustomed to researching cars will also be familiar with this dropdown navigation method.
However, there is an alternative. Edmunds.com also has a list under “Browse by make” that’s simply full of links. Clicking a link then takes you to a page with a list of cars by that make.
This has a couple advantages, especially for a research site like edmunds.
- It’s very quick to glance at that list, find the make you’re looking for, and click it.
- This has huge benefits for SEO. I attended an SEO conference hosted by the guys who optimized edmunds.com. One of the things they talked about was the great improvements they made with the link structuring. By dividing the site into landing pages for Ford > Mustang (and so on) they were able to create better long-tail SEO for searches like “Ford Mustang”, “Ford Mustang GT” or “Ford Mustang reviews.” This technique is called siloing.
The disadvantage of course is that you have to wait for the next page to load before choosing the model. So you should of course weigh your options, based on your end goals.