I've been long looking at crossing off Poland, Lithuania, Latvia, Estonia, Finland, and perhaps a tiny bit of Russia (around the Gulf of Finland, hang out a bit in St. Petersburg, continue on to Finland).
Though I'm not a "fair weather rider", my previous hopes to head up there have been thwarted by weather reports of 2+ solid weeks of miserable weather (while other parts of Europe were to see unleashed sunshine and unicorns). Hopefully this summer, the weather will be nice and I'll finally get to check them out.