You can find the last national official data catalog from http://data.suomi.fi which will be populated and further developed during the contest.

For the purposes of this contest and the Finnish Open Data developer community we will launch also a new more developer oriented catalog site http://opengov.fi/ on 30th of May (currently there is only a test version of the site running).

Apps4Finland participants may use any available data sources, but the used datasets should be announced at the opengov.fi website, so that the others get to know the same data sources. Both catalogs (data.suomi.fi and opengov.fi) will contain the official public data sets from Finland, but the opengov.fi is wider and all kinds of useful APIs and dataset (i.e. open streetmap) can be recorded there.