Against a background of the low engagement of SMEs in e-business this paper investigates the emergence of innovative critical e-aggregation applications defined as an e-business application, promoted by a trusted third party, which engages a significant number of SMEs by addressing an important shared business concern within an aggregation. By a review of secondary data and empirical investigation the research shows that such applications can facilitate the engagement of SMEs in e-business. There are three key findings, namely: the emergence of aggregation specific e-business applications; the emergence of collaboratively based one to many service provider business models; and the importance of trusted third parties in facilitating the adoption of higher complexity e-business applications by SMEs. Significantly this work combines both user and provider perspectives in order to provide a rich contribution to the already considerable literature on SMEs and ICT. The findings will be relevant to academic researchers, service providers and policymakers assisting them in understanding some of the complex issues affecting the engagement of SMEs in e-business