Be careful if you choose to work with either AdOrigin or Everyone.net (both suggested by illusivedaze above). These companies have both attracted more negative feedback than the bulk of their peers, and thus should not be relied upon as a core source of revenue.
While you have little to no traffic, you can get a few programs in place. ClickXchange and the lead-based networks come to mind. And, in the case of ClickXchange, a selection of CPM-based programs are made available to you from the get-go.
Once you have acquired a larger audience of predominently US-based visitors, FastClick, DoubleClick (soon to be MaxWorldwide), BurstMedia, 24/7 Real Media, Tribal Fusion, Adtegrity, ValueAd, Advertising.com and ValueClick are all worth considering.
Of course, the CPC-centric networks are also worth a look. Often, these can produce returns in excess of those provided by the average CPM exchange during these times in which direct marketing still rules the roost over branding-style campaigns.
