LINK HARVESTER
Link Harvester is a very powerful free tool for finding the backlinks to any given site. Rather than just list backlinks, you will be able to see which links have common Class C IP address blocks. It also breaks down results into unique linking domains (i.e. multiples links from any given domain are discounted), links from .gov, .mil, .edu or .ac.uk domains, and other useful criteria too.
The common class C Ip address block information is useful for getting an indication of how many links might be from the same server and hence possibly from the same organisation. It is likely that Google discounts multiple links that all seem to come from the same source.
The output from the tool can be formatted to CSV so it can be opened by spreadsheet programs.
Alcander is a mirror for this great tool, meaning that more people can use it before the daily limit imposed by the Yahoo! API is reached.