A quick post to log a quick, two line hack to the searchfeedr code to demonstrate how it can be used to search over pages that link to a given URL. Here's the demo: linkSearch.
The service works by taking a supplied URL and using the Yahoo! SiteExplorer API to find all the pages that link to it.
These links are then used to limit the search, along with an additional limit that excludes the target URL from the search results.
Now what other search limiting sources are there out there, I wonder?
PS: how about searching over links related to a particular page? Here's an example - relatedSearch. This makes use of the delicious related links service, as exposed by similicio.us. I then pipe the similicious results through a Dappit app (here) to get an RSS feed that I convert to JSON via the xoxotools rss2json service; (I couldn't parse the Dapper JSON output for some reason?).
These links - i.e. the ones related to the given URL (as suggested by delicious) - are then used to limit the search :-)