1. Slovenia
2. Germany
3. Isle of Man
4. Belgium
5. Switzerland (1.2% tax)
6.
7.
8.
9.
Any others yet?
As a side note, we joke about citizenship, but I see no reason why it wouldn't make sense to do two things immediately: Work on citizenship (dual?) and set up a bank account there. If you are going to cash out large quantities, you'll want a bank account that has some longevity and activity, so as to avoid questions from the bank. No reason why you wouldn't set that up now and begin accruing longevity.
As for citizenship, do you have to renounce your US (or other) citizenship to get citizenship in one of these other countries? I mentioned "dual citizenship" because I've heard of such a thing. Know nothing about it though...
-Burger
Are you sure that if in Germany you buy 5,000 in bitcoins and after some time you cashout 50,000 you have 0% to pay? No capital gains tax? No other tax? I don't think is that easy.