Burlingame, Calif.-MarketMakers Inc., Burlingame, Calif., said Monday that it has launched marketmakers.com. Aimed at marketing executives, the site is a portal that offers such services as competitive overviews, e-mail notifications of company news and job postings. A referral database, listing vendors that have proven themselves with marketing executives, is a key feature, said Jennifer Kammeyer, VP-marketing for MarketMakers Inc. The site will be supported by a cut of revenues from sales it helps generate. Initial sponsors include Market Tools Inc.'s Zoomerang, PlaceWare Inc. and Responsys.com.