I'd recommend
Intermedia for private label reselling. While I have a reseller account, I've never used it (or needed it). I say that only to say this: they are on the ball. Despite having never done a thing with my account, I get regular communications with system status updates, services updates, et al *and* you get an account manager much like iWeb does. I'm a C# and ESX/Citrix admin so hosted services really don't carry very much appeal for me, but if you are looking to resell Exchange 2k7, Intermedia is the place to go, IMHO. Don't go to Intermedia.com - different company. :-)