1. Arctic Bell Heather
2. Dwarf birch
Fantastic fuel - Burns like petrol (Well, relatively speaking)
This was the best fuel I found. However, I only found far up north near Abisko. It is also recommended as fuel in the arctic in John Wiseman's book on survival.
This is a very common plant in the Scandinavian mountains. It is present almost everywhere, except the high alpine areas. Birch branches contain some kind of oil which means they burn pretty well even when moist.
Black crowberry. take the dry grey branches. Photo by Ante Aikio from Creative Commons.
There are probably a lot of other fuels available. Willow will probably work very well. According to a Saami man in Yngve Ryds book you can even light green willow directly if slice it thinly. Juniper bushes should also be very good. The best bushes are often found next to rocks.
Beyond the limit
If you go really high up there is almost no vegetation at all available. For these circumstances you need to either bring fuel from the valley or perhaps use Esbits. Four small Esbits should be enough to boil 8dl of water. The pot stand on top of the Bushbuddy works quite well as an erzats Esbit stove. A big thanks to Harald Igesund for this valuable tip. In the future I will try to publish some pictures on this setup.