A great place for researching mobile payment solutions

The ePayments Systems Observatory is a great starting place for unearthing information about mobile payment solutions:

The ePSO inventory is a database on electronic payment systems, related projects and initiatives. Its geographical scope is Europe, but relevant activities outside Europe are also sometimes taken into account in a selective way (e.g. innovations). Although the focus is on payment inititiatives, also several interoperability, technical and strategic initiatives are included.

It includes a search facility, which is great if you want to search for specific terms. If instead, you want to see solutions by country, topic or system name, try this one. Finally, it includes some interesting papers.