Since this one has picked up again, I'll throw my bit in, especially as I don't have any special interest.
Firstly, as pointed out previously, decide where you want to go, because walking in Norway is going to be rather different from Greece. Secondly, check out magazines like TGO and Trail as they frequently run articles on treks abroad.
Once you have a good idea, get hold of a copy of the Rough Guide and/or Lonely Planet guide for the area. Lonely planet often do 'Walking in ...' books which give you walking ideas, while Rough Guide specialise more in places to stay, campsites etc.
As Walkinggirl has already mentioned, you should be able to get these, and maps, from Stanfords. While mentioning maps, it is worth noting that for some parts of Europe these can be appalling, for example a map I was forced to use of Crete could not be used with a GPS, some of the detail was incorrect, there were no gridlines and the best scale I could get was 1:100000, so if you want to go to the wilder parts of Europe you may need a good guide book specific to the region you want to walk as well.
S.