Finland:
Bombina variegata. Breeding. Just heard about this a few days ago.
Lacerta agilis. Breeding.
Pelophylax lessonae*. Breeding and spreading.
Pelophylax ridibundus*. Breeding and spreading.
Ichthyosaura alpestris. Breeding. Significant potential for spreading.
Hyla sp. Can't remember whether meridionalis or arborea. Apparently not breeding, but overwinters in someone's garden.
Most of the species are found in a narrow region in the south-west, which is a bit dodgy. All species are very likely deliberate releases, but accidental introduction of some species is possible as there are a lot of plant-importing greenhouse-farmers down there.
* The origin of the Pelophylax sp. is being worked on. Also, the species IDs aren't all clear.
That's a big bunch of introduced species for a country with 10 indigenous herp species.