I built a similar site search engine at www.lovelygrape.com. Please have a try and leave suggestions. The following is some search examples.

lovelygrape.com/search.php?URL=tools.seobook.com
lovelygrape.com/search.php?URL=http://www.informatik.uni-trier.de/~ley/... (Similar sites to DBLP Bibliography）

lovelygrape.com/search.php?URL=www.nature.com/nature/index.html (similar sites to nature magainze）
lovelygrape.com/search.php?URL=piano+sheet
lovelygrape.com/search.php?URL=http://www.slickdeals.net/
lovelygrape.com/search.php?URL=www.monster.com (job search sites)
lovelygrape.com/search.php?URL=http://coolmath4kids.com/ (children's math game sites)

Nice search engine, works fine. But just keep the searched keyword in the field, till the user need to change for further search. Now it clears the text which has been searched, check it out..

Nice site.......

All the best for future........

I searched my site and most my competitors showed up. I think you have a good tool there.

wow! very unique site. works better than expected.