Sleek, modern, loads of infografics...probably the best statistic site out there
...and forget about the beta ;-)
the only useful online tool for crating map strategies/tactics
The official information resource from Wargaming for all tanks
I know, I know, this is for the "proper" World of Tanks. But most of it is perfectly adaptable and helpful also for WoT Blitz (apart from the arty tips and the maps...duh)