Where do I find marketing firms to help me promote my site?

I want to promote my site but does it make sense to outsource the marketing efforts to a full-time firm or do it myself?

I'm launching a social platform with an e-commerce component. Would it make sense to hire a marketing firm to help promote the social site and bring in users or try to do it myself? I have a small marketing budget but perhaps I can raise more money to spend on the marketing firm services?

Marketing is an important part of any Small to Medium business venture, as you know. It's not always necessary to hire an outside firm, if you know how to best target your audience to your social site.

There is a great video currently on the Microsoft Small Business Center regarding this very subject, you might want to take a look at it and other areas on that site if you haven't already done so. The video is on the very top of the front page in the "Featured Video" area.

The site doesn't require any registration, so it might be worth your time to check it out before you spend money on outside marketing.

Microsoft Start-Up Center:
http://www.microsoftbusinesshub.com/

You need to provide way more information for any of us to provide much guidance. What industry are you in? What is your site/application? Who are you marketing it to? What are your forecasts for usage/sign ups/revenue? What kind of budget do you have? What is your expertise - are you a marketer? What type of marketing do you envision for the site?