Sufyan created a free tool which checks page similarity. You can set it to check sitewide on small sites, or enter in a couple URLs manually to cross check them for how similar the pages are to one another.
This tool doesn't test if a site has canonicalization issues, but it is plenty cool for free.
update: link to seojunkie.com/2006/05/24/site-wide-duplicate-content-analyzer/ removed as it is now a domain lander page
If I could sell 10 on this site it would amount to about $5,000 a month in passive supplemental income. I would be more likely to try to sell just 1 exclusive for something like that price though :) The tool's goals might be a bit self serving, and the actual link value might vary from what the tool reports, but it could be a helpful tool to people new to SEO looking to price the value of a link.
Jim Boykin recently mentioned that Text Link Brokers created a link building wiki. You know the market is getting more competitive when you got all the link brokers creating free tools and resources :)
Google made their AdWords traffic estimator available external to your AdWords account. They still use the evil little graphical representation for total search volume, but they give rough approximations in actual numbers for the amount of AdWords clicks they think you will receive.
If you do not enter a bid price or budget the bid price they recommend is supposed to show your ads ranking #1 85% of the time. More background here. They also note that when you access this tool external to your account that it will not factor in your past account performance, so the numbers may not be as accurate as if you use the tool in your account.
RustyBrick pointed out a new free SEO tool by Sufyan that searches through a page or site to look for links to sites that are banned in Google. It is designed for smaller to mid sized sites. The tool returns a list of pages you link at and their PageRank. The tool lists the age and URLs of pages that do not appear in Google.
Most large quality sites probably have at least a few links to banned sites, so you don't want to let Google become the editor of your site, but if most of your links go to banned sites that could hurt your site's reputation or ability to rank in Google.
Currently Google is also a bit flaky on the URL search. With some of them they they give the signs of sites being banned while listing many pages if you do a site: search.
Google extends their lead in the keyword research market by adding a new tool called Google Trends. It operates similar to the Google keyword research tool, but offers trends that goes back for years, and even overlaps news related to keyword search spikes, like Google Finance does. Many of the links they provide are to cheesy press releases, so that might present another marketing opportunity.
The tool also shows top cities, regions, and languages that queries occurred in. They also allow you to set timeframes and the market location.
It also allows you to compare phrases.
The only downsides to Google Trends are that it only works for broad terms and does not give exact numbers.
Tag Viewer is a Ruby on Rails AJAX application that makes it easy to cross reference tagged resources at popular tagging sites.
The idea sorta came to life after I started to find the footer tag links on my keyword research tool rather handy. Your thoughts on Tag Viewer would be appreciated.
I don't intend to commercialize Tag Viewer in any way. I had it made because I think it will be useful for helping me do web research. While I claim to be an SEO, I am much more of an info porn junkie than an SEO ;)
Google recently opened up their AdWords keyword research tool by allowing it to be accessible from outside AdWords accounts. They also added seasonal search volume data for global and local searches, and allowed it to be accessible by match type (ie: broad, phrase, exact).
That will likely just about kill off most of the paid keyword research tool market.
I told MSN that I thought one of the ways they could possibly catch up a bit with Google on the SEM front is to make the default keyword research tool. Google's now is feature rich, shows seasonal data, data by match type, and the data is easy to export. As Google, Yahoo! and MSN jocky for position you can bet that their keyword research tools are only going to get better - although I don't think Yahoo!'s crusty old tool has changed in about a decade hehehe.