Online mortgage lenders are signing up with the largest Internet portals to boost their business. American Home Mortgage’s MortgageSelect.com division has become the only integrated mortgage provider on Microsoft’s MSN HomeAdvisor online home and real estate guide. Meanwhile, LendingTree is teaming up with Yahoo!Finance. The exclusive, multi-year agreement with MSN enables HomeAdvisor to feature MortgageSelect.com's loan products and tools.