seologs.com is very incomplete for my server. MSN also has this feature in its search bar but I cannot recall the prefix required. webhosting.info can also reverse lookup.
I believe for MSN & webhosting.info that it is not "real time" but they are looking up a in a database that they build/maintain for other purposes and this is just a by-product. IE: MSN would have the IP of all sites in their search database & Webhosting.info belongs to registrar Directi.