Alexa Research
Is it me or nobody will give you a quote on the web? Being forced to e-mail someone to know how much as service costs deters me. Pricing opacity makes me think I'll be overcharged, so I won't even inquire about it at all. Missed opportunity, and a shame since I'd like have access to the deep-range version of this radar.
08/04/01 update: I've forgot to mention it here, but the "radar" link from Alexa is dead because they stopped their free service (it let users see what sites gained or lost most traffic from month to month).