What kind of reputation are you talking about? within your company, or outside your company?<p>Internal - Use Hard Metrics.
If you are the marketing team and have an influence on the final sale (ie:Your clicks convert to paid subscribers/purchases) then proving how you brought home the bacon, is a good metric to use.<p>In bigger enterprise type environments - show how you can automate and mature marketing processes.<p>External - Offer Something
Tweet, blog about your work, speak at conferences, attend user groups for marketers.... I know people who have built good career paths based on their perceived expertise from a few talks at marketing conferences. These are some ways to build your reputation externally.