Yahoo Site Explorer has been shut down!
So what alternatives do we have?
Unfortunately none that adequately substitutes what Yahoo! Site Explorer used to offer, and that is a reliable count of the backlinks of a site (including a list of said backlinks).
Google has the “link:domain.com” query, which is supposed to show the backlinks of a site, but only displays a very small sample of the backlinks, to avoid people reverse engineering Google’s algorithm.
If you want to see the backlinks of sites you own the best bet is Google Webmasters Tools.
If you want to see the backlinks of sites you don’t own you can try using the Open Site Explorer, which is a tool created by the SEOMoz guys. It track much fewer links that what Yahoo! used to, but as far as I know it’s the best alternative online.
What about you, what tool do you use to check the backlink of a given website?