SEo Quake is free tools that provide u enough information & help u analyzing your site. have u know other seo tool that are free
mcdar.net = McDar Keyword Analysis Tool 123promotion.co.uk = Keyword Popularity Tool elixirsystems.com = Link Quality Assessment
Seo Quake is really good. There is lot of Firefox plugins available for SEO purpose. You can find out some more free tools in webconfs.com
SEO Doctor is also a good tool for webmaster. SEO Doctor allows easy SEO diagnosis and problem solving for webmasters.
is there any tool for SERP checking. I was using linkextend this before but now it has stop giving the no so can't check my SERP
I like SEO Quake and its really an effective tool for SEO but I also like Google Analytics, Site explorer, SEO Digger a little tool that shows what keywords you're currently ranking in SEO are some tools which can be helpful for SEO .