How to use subdomains to represent sections?

You should use the request_routing plugin from Dan Webb.

http://agilewebdevelopment.com/plugins/request_routing

Best regards

Peter De Berdt

You should use the request_routing plugin from Dan Webb.

http://agilewebdevelopment.com/plugins/request_routing

I dont want to do tickets.whatever.com/tickets/some_controller

This requirement makes request_routing inappropriate.
Ben asking for mapping subdomain to controller name, while
request_routing provides a way to include subdomain in mapping
requirements.

Actually, using the request_routing plugin is a good idea, as it allows you to map to different controllers based on subdomain. I use it for exactly that purpose myself.