If you are successfull in selling domains consistently then why not make it a profession and become a full-fledged business .?
Setup a website or EBay store to showcase all your domains. Setting up a ecommerce website can be very easy and it can cost you as low as $100 - $500. If you have programming skills then you can use opensource content management systems like Zencart or Drupal to build your own ecommerce shop.
Provide a great customer service that will build your reputation, and make sure that you’re following all the business rules that apply, such as registering, taxes etc.