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)

pretty kewl, i checked out, you did a good job!!!

Thank you for trying out! The name of the site is change to (to avoid confusion :-) :
http://similar-site.com/

I like it! Very useful.

Thank you all! I made updates to the site. I wish I were a better interface designer. Planning to develop visual browsing with flash. It's my research project. New url: http://similar-site.com/

Dont use flash, or visual browsing
unless there is a working alternative on the site
cant use flash, its not accessible,
wouldn't use flash its slow and overhead intensive

It works, dont break it
for inspiration,

google empty search screen, nothing except what is required to make it work

makes $$$$$$$$$$$$$$$$$$$

Yahoo, search pane is a tiny part of a page full of BS, flash, images, rss, page takes forever to load

loses $$$$$$$$$$$$$$$$$$$

We recently made significant improvements to the searching algorithm. It gives much better results than before. The main page also shows some examples of similar site search and tag search. Please visit http://similar-site.com/