The under-use of spectrum offers new perspective for a secondary usage of the spectrum. However, this can be achieved at the expense of a tight spectrum sharing control and management between the different involved parties (operators and users). This paper presents the latest research achievements of a major European research initiative (E2 R project) in the field of flexible spectrum management. Both the economic and technical aspects are addressed in the specific case of collaborative based secondary spectrum usage. The paper approaches the spectrum sharing problem with a distributed control and management solution perspective, paving the way towards first insights of a cognitive radio based solution. Firstly, two approaches for a market based spectrum sharing, including the bidding and pricing incentives, are presented. Secondly, the achievable capacity gains and the underlying spectrum sharing coordination processes to manage the cochannel interference are presented. For each of the economic and technical aspects, concepts, related results and analysis are included. Finally, an outlook on the objectives of the phase-2 (2006-2007) of the project in the field of flexible spectrum management including the spectrum measurement campaign is presented