Obviously Nicolay Valuev is the top of the pile. Then who? Isn't Vitali something like 6'8? What about protected bums like Fields and Faruq Saleem? Aren't they around 6'7? Big Time McCline is around 6'6... Who else is touching the clouds?
Danish newcomer Morten Poulsen is 7'1 (219 cm) Here is a link to a danish video with him: http://ekstrabladet.tv/sport/article1064091.ece (BTW: He is officially the tallest man in Denmark...)
Henry Akinwande is 6'7 and still boxing in spite of being 43. Lance Whitaker is 6'8 and won a couple of easy fights this year, after being inactive since getting stopped by Sultan Ibragimov in 2005. Germany's Timo Hoffmann is 6'7 1/2 (he's the only fighter to take Vitali the full distance, back in 2000).Undefeated Alexander Ustinov (12-0-0), from Belarus, is also 6'7 1/2 and recentrly stopped Julius Long inside one round in what might be the pro fight with the biggest combined height ever made (a 6'7 1/2 fighter vs a 7'1 fighter), beating Mccline(6'6) vs Valuev (7'0), altough Mccline-Vluev is still on top as a title fight.
He dropped a 6 rds decision last summer in Turkey, and still gets ranked (at #72) by boxrec, so its safe to asume he's not retired.
alexander dimitrenko comes to my mind as a very effective, tall HW. he's a solid 6'7", so he probably doesn't fall into the the same category as the 7 footers, but he's still a big man. he carries his size/height better than wlad imo. i'm not saying he'd beat wladimir klitschko by any means as he doesn't hit anywhere near as hard, nor does he posess the same strength and imposing size despite being the same height. i'm just saying he has movements comparable more to a cruiserweight as oppose to the giant robotic HW's. he throws more combos and can fight on the inside as opposed to wlad.