Ubiquitous computing places humans in the center of environments saturated with computing and wireless communications capabilities, yet gracefully integrated, so that technology recedes in the background of everyday activities. The ubiquitous computing world then, is a world largely defined by applications. But such applications present an altogether new set of requirements. The special track on ubiquitous computing applications, first introduced in ACM SAC 2004, provides a forum for the discussion of all types of ubiquitous computing applications and related specialized infrastructures built for the deployment of targeted applications. Individual papers place applications within their use context and introduce novel and appropriate interaction paradigms while at the same time addressing related technical and business aspects and consequently identify novel opportunities or constraints.